Termbank
  1. A
    1. Abstraction
    2. Alias
    3. Argument
    4. Array
  2. B
    1. Binary code file
    2. Binary number
    3. Bit
    4. Bitwise negation
    5. Bitwise operation
    6. Byte
  3. C
    1. C library
    2. C-function
    3. C-variable
    4. Character
    5. Code block
    6. Comment
    7. Compiler
    8. Complement
    9. Conditional statement
    10. Conditional structure
    11. Control structure
  4. D
    1. Data structure
    2. Duck typing
  5. E
    1. Error message
    2. Exception
  6. F
    1. Flag
    2. Float
  7. H
    1. Header file
    2. Headers
    3. Hexadecimal
  8. I
    1. Immutable
    2. Initialization
    3. Instruction
    4. Integer
    5. Interpreter
    6. Introduction
    7. Iteroitava
  9. K
    1. Keyword
  10. L
    1. Library
    2. Logical operation
  11. M
    1. Machine language
    2. Macro
    3. Main function
    4. Memory
    5. Method
  12. O
    1. Object
    2. Optimization
  13. P
    1. Parameter
    2. Placeholder
    3. Pointer
    4. Precompiler
    5. Precompiler directive
    6. Prototype
    7. Python console
    8. Python format
    9. Python function
    10. Python import
    11. Python list
    12. Python main program
    13. Python variable
    14. Python-for
    15. Pääfunktio
    16. printf
  14. R
    1. Resource
    2. Return value
  15. S
    1. Statement
    2. Static typing
    3. String
    4. Syntax
  16. T
    1. Terminal
    2. Type
    3. Typecast
  17. U
    1. Unsigned
  18. V
    1. Value
  19. W
    1. Warning
    2. while
Completed: / exercises

Input / Output

Learning Objectives: Using I/O pins programmatically for various purposes in embedded devices.
Input / Output, commonly referred to as I/O, refers to the transfer of information between a computer's components and peripherals. Inputs are signals/data received by any component, such as a button press or a message from a peripheral. Outputs are signals or information sent by electronic components, such as a control signals to a peripheral device (e.g PWM signal to control a motor).
Embedded devices typically come with built-in physical components and control logic on the microcontroller and circuit board to handle I/O. Below is a list of common components, some of which will be used in this course:
Peripherals are either digital or analog. Digital components are often more complex, using different data buses, and are managed using bit values (i.e., agreed-upon voltage levels).
Analog components provide voltage values that can range between ground and the operating voltage (e.g., 0-5V). For example, many simple sensors represent their measurements as analog voltages. Of course, analog signals must first be converted to digital values (numbers) before a computer can process them. Microcontrollers have built-in analog-to-digital converters (ADCs) that convert voltages into (rounded) numerical values with a set precision, for example, using an 8-bit scale (0-255). The programmer's task is then to convert the ADC's value to correspond to a real-world measurement, which can then be processed in the program.
Examples of such sensors include various temperature, pressure, and light intensity sensors, as well as analog microphones. For instance, if a temperature sensor has a measurement range of 0-100°C, the programmer would need to create a conversion function that converts the ADC value (0-255) to a temperature value (0-100°C). This can then be displayed to the user, such as showing that the room temperature is +21°C.
In the SensorTag, the integrated sensors are primarily digital (more on this later), but the analog components include LEDs, whose brightness can be adjusted using PWM.

Pins

Okay, let’s start with the basics. Pin refers to the physical lead or connector of a microchip or component. The purpose of pins is to provide both electrical and mechanical connections to the circuit board. Each pin or lead has a specific purpose. The pinout defines the functions of each pin. As you’ll notice, sometimes a pin has multiple purposes, depending on the device's functionalities. This means that a device’s operation is limited to using only one of these functions at a time.
For example, below is a description of the pins on the Intel 4004 (the world’s first commercial microprocessor from 1971).
"Intel 4004, the world’s first commercial microprocessor"

Pins and Bits

Let’s review a bit :-p from the previous Bit Operations lecture material. The general principle is that in the program code, each pin of a peripheral or microcontroller corresponds to a single bit, which we manipulate using C language bitwise operations.
To simplify the programmer’s (and electronics designer’s) work, each pin is given a logical name associated with its function, such as RESET or IO_16. These names usually align with the peripheral library names, and they represent constants that we use to perform bitwise operations on the corresponding bit.
Example: Resetting a device by clearing (setting to 0) the RESET bit in the device’s control register. (Normally, you can’t reset a device directly from the program, but it makes for a dramatic example...)
   control_register = control_register & ~(1 << RESET);
Some pins are designated as general-purpose (General Purpose I/O, GPIO), and the programmer is free to define their purpose, depending on what peripherals are connected to them. Logically, in microcontrollers, GPIO pins are sometimes grouped into I/O ports, so that, for example, 8 pins are treated as a single port. This is convenient if the device requires multiple I/O lines, as they can be logically handled as a single unit and managed easily as binary values. However, SensorTag treats all I/O pins as individual unless the programmer defines logical ports for the desired pins. This is not needed for the course project.

Memory-Mapped I/O

Memory-mapped I/O means that we reserve memory locations in the device's central memory as (device) registers connected to the peripheral's pins. By manipulating the bits in these registers through variables in the program, we interact with the peripheral. The memory locations can be seen as representing the data, address, and control buses required by the peripheral, based on the device’s needs:
Registers come in three types: address, control, and data registers. A peripheral may offer several registers of each type, or any combination of these types depending on the device’s implementation. For example, with SensorTag, we might need dozens of registers to operate a more complex peripheral. It’s quite a relief to have pre-made libraries for working with peripherals!
For each of these registers, we need to know:
As an example, here’s one register description from SensorTag. This peripheral (a circuit monitoring the battery voltage) has a data register that contains the battery voltage. A very useful register, indeed!
Battery monitor register
The image shows that the register size is 32 bits (31-0, the yellow field in the image). It’s noted that bits 31-11 are reserved for internal use by the device, but the other bits contain information relevant to us:
Now, if we want to know the battery voltage, we would query this memory-mapped data register and convert its value into a floating-point number, for example. SensorTag’s RTOS provides a macro for reading and writing register values called HWREG.
uint32_t battery_voltage = HWREG(AON_BATMON_BASE + AON_BATMON_O_BAT);
In this case, we obtain the register’s memory address by adding the base address reserved for battery voltage monitoring (AON_BATMON_BASE) to the register’s offset within that memory area (AON_BATMON_O_BAT).

Datasheet

The manual for a component or microcontroller, known as the datasheet, provides an extremely detailed description of the internal workings and every integrated circuit. The datasheet serves as a reference when programming the hardware.
Datasheets are typically written in English, use highly specialized terminology, and are hundreds or even thousands of pages long for more complex devices. Even the datasheet for the relatively simple 8-bit Arduino microcontroller is almost 300 pages! So, while controlling pins on Arduino seems simple, there are dozens of pages in the datasheet that the programmer may not need to know about. For more complex devices, there may be additional manuals along with datasheets, such as the SensorTag Technical Reference Manual. This handbook has 1743 pages!
Fortunately, instead of combing through hundreds of pages of datasheets, development environments provide libraries, functions, macros, and constants that implement peripheral control and higher-level functions for us.

A Look into SensorTag

The image shows a block diagram of the functionalities of SensorTag’s microcontroller (TI Simplelink CC2650 Wireless MCU). As seen, the CC2650 is quite a versatile and complex device. It even integrates two separate ARM Cortex cores, each with its own program and RAM memory. The more powerful one (Main CPU, Cortex M3) is used for running user programs, while the other (Rf Core, Cortex M0) is dedicated solely to wireless communication. SensorTag is designed so that both cores are programmed separately and independently of each other. This has the advantage that the device's wireless communication protocol stack (wireless technology) can be swapped without affecting the user’s program.
"CC2650 Wireless MCU"
Below is a description of the pinout for SensorTag’s microcontroller (TI CC2650). Pins are given logical names by the programmer (and electronics designer) to simplify their use, such as RESET_N or DIO_16.
Some pins are designated for general purpose use (General Purpose I/O, GPIO), and the programmer can freely define their purpose, depending on the peripherals connected to them. In SensorTag, during the design phase of the device, some GPIO pins have already been reserved for connecting peripherals to the microcontroller, which, of course, dictates their usage.
"CC2650 Wireless MCU pinout"
In SensorTag, the RTOS libraries provide us with these constants and pre-made function calls to programmatically use the pins.
Below is an example of constants defined for SensorTag’s I/O pins in header files. We can use the logical name of the pin in the code through these constants provided in the header files. For example, we can use the constant IOID_18 to refer to the physical pin DIO_18, and then change the logical value of the corresponding bit in the code using bitwise operations. Convenient!
#define IOID_18                 0x00000012  // IO Id 18
#define IOID_19                 0x00000013  // IO Id 19
#define IOID_20                 0x00000014  // IO Id 20

Using I/O Pins

Next, we will explore using I/O pins in SensorTag with a code example. The available SensorTag-specific constants can easily be found in the header files that automatically appear in our software project Board.h and CC2650STK.h.
In the example below, we use one of SensorTag’s two buttons as an on/off switch for one of the device’s LEDs. This means we need to define two pins for the program to use: one for the button and one for the LED.
We will use the pre-built Pin library provided by the compiler environment. Since certain I/O pins in SensorTag are pre-wired to the buttons and LEDs, we can include their configurations in the code by using the PINCC26XX.h header file. To activate the button in the program, four things must be done:
  1. Declare global RTOS variables for initializing and handling the button.
    • In this example, buttonHandle, buttonState, and the array buttonConfig[].
  2. Initialize the physical buttons as desired.
    • In this example, the array buttonConfig[].
  3. Write a handler function for the button press.
    • In this example, the interrupt handler function buttonFxn.
  4. Finally, use the library functions in the main function to activate the I/O pins corresponding to the buttons.
Note! The SensorTag has two buttons and two LEDs. These definitions must be made separately for each pin. So, if we want to use all of them, we need to write four declarations and initializations in the code.
In this example program, each time a button is pressed, the function buttonFxn is executed, which toggles the state of the pin corresponding to the LED, thus turning the device’s LED on or off. The example is broken down below.
#include <ti/drivers/PIN.h>
#include <ti/drivers/pin/PINCC26XX.h>
...
// RTOS global variables for handling the pins
static PIN_Handle buttonHandle;
static PIN_State buttonState;
static PIN_Handle ledHandle;
static PIN_State ledState;

// Pin configurations, with separate configuration for each pin
// The constant BOARD_BUTTON_0 corresponds to one of the buttons
PIN_Config buttonConfig[] = {
   Board_BUTTON0  | PIN_INPUT_EN | PIN_PULLUP | PIN_IRQ_NEGEDGE, 
   PIN_TERMINATE // The configuration table is always terminated with this constant
};

// The constant Board_LED0 corresponds to one of the LEDs
PIN_Config ledConfig[] = {
   Board_LED0 | PIN_GPIO_OUTPUT_EN | PIN_GPIO_LOW | PIN_PUSHPULL | PIN_DRVSTR_MAX, 
   PIN_TERMINATE // The configuration table is always terminated with this constant
};

// Button press interrupt handler function
void buttonFxn(PIN_Handle handle, PIN_Id pinId) {

   // Toggle the state of the LED pin using negation
   uint_t pinValue = PIN_getOutputValue(Board_LED0);
   pinValue = !pinValue;
   PIN_setOutputValue(ledHandle, Board_LED0, pinValue);
}

int main(void) {
    
   Board_initGeneral();

   // Enable the pins for use in the program
   buttonHandle = PIN_open(&buttonState, buttonConfig);
   if(!buttonHandle) {
      System_abort("Error initializing button pins\n");
   }
   ledHandle = PIN_open(&ledState, ledConfig);
   if(!ledHandle) {
      System_abort("Error initializing LED pins\n");
   }

   // Set the button pin’s interrupt handler to function buttonFxn
   if (PIN_registerIntCb(buttonHandle, &buttonFxn) != 0) {
      System_abort("Error registering button callback function");
   }

   BIOS_start();

   return (0);
}
Let’s break down the example program step by step.

RTOS Variables for Pin Usage

First, we introduce a set of variables for each pin we are using, which the RTOS requires. Again, we need handles for the pins, which are declared using the Pin_Handle variable. Another variable that the RTOS needs is the pin state, which is declared using the Pin_State variable. We don’t need these variables in our own code, but we’ll keep the RTOS happy by including them.
// RTOS variables for pin usage
static PIN_Handle buttonHandle;
static PIN_State buttonState;
static PIN_Handle ledHandle;
static PIN_State ledState;
Here we declare variables for two pins, one for the button and one for the LED. For each pin, we need the two variables above: buttonHandle and buttonState for the button pin, and the same for the LED. Piece of cake.

Pin Initialization

Next, we initialize each pin as either input or output in its respective configuration table. All the constants and their purposes used here can be found in the Pin library documentation, but the following configurations are sufficient for the course.
PIN_Config buttonConfig[] = {
   Board_BUTTON0  | PIN_INPUT_EN | PIN_PULLUP | PIN_IRQ_NEGEDGE,  
   PIN_TERMINATE 
};

PIN_Config ledConfig[] = {
   Board_LED0 | PIN_GPIO_OUTPUT_EN | PIN_GPIO_LOW | PIN_PUSHPULL | PIN_DRVSTR_MAX,
   PIN_TERMINATE
};
Note that the variables buttonConfig and ledConfig are arrays with two elements. In the first element, we use a bitwise OR operation on four constants, and the second element is the constant PIN_TERMINATE.
In the first element, the constants are interpreted as follows. The first constant (configuration bit) is the identifier for the corresponding button or LED on the SensorTag, either Board_BUTTON0 or Board_BUTTON1 for the buttons, and Board_LED0 or Board_LED1 for the LEDs.
The second constant defines the pin’s purpose, i.e., whether it is used as input or output. For an input pin, we read its state (for example, whether the button is pressed or not), and for an output pin, we set its state (for example, turning the LED on or off). After all this explanation, in the example, we set the button pin as input and the LED pin as output.
The third configuration bit tells us the initial state of the pin:
In the button configuration, we also see the constant PIN_IRQ_NEGEDGE, which sets the pin to trigger an interrupt in the program whenever its state changes on the falling edge. That is, when the button is pressed, the voltage drops to ground level. Or, when the button is released, the voltage rises to the operating voltage (rising edge), and an interrupt for that can be caught using the constant PIN_IRQ_POSEDGE. More about pin interrupts will be covered in the next material.
The configuration table always ends with the constant PIN_TERMINATE.

Pin Interrupt Handler Function

For pins set as inputs, we generally need a handler function that specifies what action to take when the button is pressed, causing an interrupt. In this case, we have implemented the handler function buttonFxn.
void buttonFxn(PIN_Handle handle, PIN_Id pinId) {

   // Toggle the state of the LED pin using negation
   // Not using pointers but direct values!!!
   uint_t pinValue = PIN_getOutputValue(Board_LED0);
   pinValue = !pinValue;
   PIN_setOutputValue(ledHandle, Board_LED0, pinValue);
}
Here’s how the function works. First, we read the current state of the LED pin (on "1" / off "0") using the PIN_getOutputValue function, storing the value in the pinValue variable. This function takes the constant corresponding to the pin (Board_LED0) as its argument. Then, we negate the value, meaning we toggle the LED state between on and off. The new state is then set using the PIN_setOutputValue function.

Initializing the Pins in the Program

Next, we move on to the main function. Pins are reserved for use in our program using the Pin_open function call, which takes the RTOS pin variables and the configuration we introduced earlier as parameters.
// Initialize the LED in the program
ledHandle = PIN_open(&ledState, ledConfig);
if (!ledHandle) {
   System_abort("Error initializing LED pin\n");
}

// Initialize the button in the program
buttonHandle = PIN_open(&buttonState, buttonConfig);
if (!buttonHandle) {
   System_abort("Error initializing button pin\n");
}

// Register the button interrupt handler
if (PIN_registerIntCb(buttonHandle, &buttonFxn) != 0) {
   System_abort("Error registering button callback function");
}
The RTOS handle tasks and interrupt handler functions as equivalent functionalities. We’ll talk more about interrupts shortly, but for now, when the button’s state changes (on the falling edge, as defined by the constant PIN_IRQ_NEGEDGE), an interrupt is triggered. The function PIN_registerIntCb sets the function to be executed in response to the interrupt, i.e., the handler. In this program, the function buttonFxn is the handler for this interrupt.
Note! We could have implemented the same button state check using a superloop, continuously polling the button pin state in each iteration, and taking action if it changed. That’s another example of superloop-based design, but as we can see, the handler makes things easier.

Conclusion

Aside from memory-mapped I/O, another option is port-mapped I/O, where registers are managed through separate in and out instructions. However, this mechanism is not used by SensorTag.
But hey… based on this material, you now know how to write an embedded program that blinks an LED when it detects a button press! Is it time for cake and coffee?
?
Abstraction is a process through which raw machine language instructions are "hidden" underneath the statements of a higher level programming language. Abstraction level determines how extensive the hiding is - the higher the abstraction level, the more difficult it is to exactly say how a complex statement will be turned into machine language instructions. For instance, the abstraction level of Python is much higher than that of C (in fact, Python has been made with C).
Alias is a directive for the precompiler that substitus a string with another string whenever encountered. In it's basic form it's comparable to the replace operation in a text editor. Aliases are define with the #define directeve, e.g. #define PI 3.1416
Argument is the name for values that are given to functions when they are called. Arguments are stored into parameters when inside the function, although in C both sides are often called just arguments. For example in printf("%c", character); there are two arguments: "%c" format template and the contents of the character variable.
Array is a common structure in programming languages that contains multiple values of (usually) the same type. Arrays in C are static - their size must be defined when they are introduced and it cannot change. C arrays can only contain values of one type (also defined when introduced).
Binary code file is a file that contains machine language instructions in binary format. They are meant to be read only by machines. Typically if you attempt to open a binary file in a text editor, you'll see just a mess of random characters as the editor is attempting to decode the bits into characters. Most editors will also warn that the file is binary.
Binary number is a number made of bits, i.e. digits 0 and 1. This makes it a base 2 number system.
A bit is the smallest unit of information. It can have exactly two values: 0 and 1. Inside the computer everything happens with bits. Typically the memory contains bitstrings that are made of multiple bits.
Bitwise negation is an operation where each bit of a binary number is negated so that zeros become ones and vice versa. The operator is ~.
Bitwise operations are a class of operations with the common feature that they manipulate individual bits. For example bitwise negation reverses each bit. Some operations take place between two binary values so that bits in the same position affect each other. These operations include and (&), or (|) and xor (^). There's also shift operations (<< and >>) where the bits of one binary number are shifted to the left or right N steps.
Byte is the size of one memory slot - typically 8 bits. It is the smallest unit of information that can be addressed from the computer's memory. The sizes of variable types are defined as bytes.
External code in C is placed in libraries from which they can be taken to use with the #include directive. C has its own standard libraries, and other libraries can also be included. However any non-standard libraries must be declared to the compiler. Typically a library is made of its source code file (.c) and header file (.h) which includes function prototypes etc.
Functions in C are more static than their Python counterparts. A function in C can only have ne return value and its type must be predefined. Likewise the types of all parameers must be defined. When a function is called, the values of arguments are copied into memory reserved for the function parameters. Therefore functions always handle values that are separate from the values handled by the coe that called them.
C variables are statically typed, which means their type is defined as the variable is introduced. In addition, C variables are tied to their memory area. The type of a variable cannot be changed.
Character is a single character, referred in C as char. It can be interpreted as an ASCII character but can also be used as an integer as it is the smallest integer that can be stored in memory. It's exactly 1 byte. A character is marked with single quotes, e.g. 'c'.
Code block is a group of code lines that are in the same context. For instance, in a conditional structure each condtion contains its own code block. Likewise the contents of a function are in their own code block. Code blocks can contain other code blocks. Python uses indentation to separate code blocks from each other. C uses curly braces to mark the beginning and end of a code block.
Comments are text in code files that are not part of the program. Each language has its own way of marking comments. Python uses the # character, C the more standard //. In C it's also possible to mark multiple lines as comments by placing them between /* and */.
A compiler is a program that transforms C source code into a binary file containing machine language instructions that can be executed by the computer's processor. The compiler also examines the source code and informs the user about any errors or potential issues in the code (warnings). The compiler's behavior can be altered with numerous flags.
Complement is a way to represent negative numbers, used typically in computers. The sign of a number is changed by flipping all its bits. In two's complement which is used in this course, 1 is added to the result after flipping.
Conditional statement is (usually) a line of code that defined a single condition, followed by a code block delimited by curly braces that is entered if the condition evaluates as true. Conditional statements are if statements that can also be present with the else keyword as else if. A set of conditional statements linked together by else keywords are called conditional structures.
Conditional structure is a control structure consisting of one or more conditional statements. Most contrl structures contain at least two branches: if and else. Between these two there can also be any number of else if statements. It is however also possible to have just a single if statement. Each branch in a conditional structure cotains executable code enclosed within a block. Only one branch of the structure is ever entered - with overlapping conditions the first one that matches is selected.
Control structures are code structures that somehow alter the program's control flow. Conditional structures and loops belong to this category. Exception handling can also be considered as a form of control structure.
Data structure is a comman name for collection that contain multiple values. In Python these include lists, tuples and dictionaries. In C the most common data structures are arrays and structs.
Python's way of treating variable values is called dynamic typing aka duck typing. The latter comes from the saying "if it swims like a duck, walks like a duck and quacks like a duck, it is a duck". In other words, the validity of a value is determined by its properties in a case-by-case fashion rather than its type.
An error message is given by the computer when something goes wrong while running or compiling a program. Typically it contains information about the problem that was encountered and its location in the source code.
An exception is what happens when a program encounters an error. Exceptions have type (e.g. TypeError) that can be used in exception handling within the program, and also as information when debugging. Typically exceptions also include textual description of the problem.
Flags are used when executing programs from the command line interface. Flags are options that define how the program behaves. Usually a flag is a single character prefixed with a single dash (e.g. -o) or a word (or multiple words connected with dashes) prefixed with two dashes (e.g. --system. Some flags are Boolean flags which means they are either on (if present) or off (if not present). Other flags take a parameter which is typically put after the flag separated either by a space or = character (e.g. -o hemulen.exe.
Floating point numbers are an approximation of decimal numbers that are used by computers. Due to their archicture computers aren't able to process real decimal numbers, so they use floats instead. Sometimes the imprecision of floats can cause rounding errors - this is good to keep in mind. In C there are two kinds of floating point numbers: float and double, where the latter has twice the number of bits.
Header files use the .h extension, and they contain the headers (function prototypes, type definitions etc.) for a .c file with the same name.
Headers in C are used to indicate what is in the code file. This includes things like function prototypes. Other typical content for headers are definition of types (structs etc.) and constants. Headers can be at the beginning of the code file, but more often - especially for libraries - they are in placed in a separate header (.h) file.
Hexadecimal numbers are base 16 numbers that are used particularly to represent memory addresses and the binary contents of memory. A hexadecimal number is typically prefixed with 0x. They use the letters A-F to represent digits 10 to 15. Hexadecimals are used because each digit represents exactly 4 bits which makes transformation to binary and back easy.
In Python objects were categorized into mutable and immutable values. An immutable value cannot have its contents changed - any operations that seemingly alter the object actually create an altered copy in a new memory location. For instance strings are immutable in Python. In C this categorization is not needed because the relationship of variables and memory is tighter - the same variable addresses the same area of memory for the duration of its existence.
When a variable is given its initial value in code, the process is called initialization. A typical example is the initialization of a number to zero. Initialization can be done alongside with introduction: int counter = 0; or separately. If a variable has not been initialized, its content is whatever was left there by the previous owner of the memory area.
Instruction set defines what instructions the processor is capable of. These instructions form the machine language of the processor architecture.
Integers themselves are probably familiar at this point. However in C there's many kinds of integers. Integer types are distinguished by their size in bits and whether they are signed or not. As a given number of bits can represent up to (2 ^ n) different integers, the maximum value for a signed integer is (2 * (n - 1))
Python interpreter is a program that transforms Python code into machine language instructions at runtime.
The moment a variable's existence is announed for the first is called introduction. When introduced, a variable's type and name must be defined, e.g. int number;. When a variable is introduced, memory is reserved for it even though nothing is written there yet - whatever was in the memory previously is still there. For this reason it's often a good idea to initialize variables when introducing them.
Iteroitava objekti on sellainen, jonka voi antaa silmukalle läpikäytäväksi (Pythonissa for-silmukalle). Tähän joukkoon kuuluvat yleisimpinä listat, merkkijonot ja generaattorit. C:ssä ei ole silmukkaa, joka vastaisi Pythonin for-silmukan toimintaa, joten taulukoiden yms. läpikäynti tehdään indeksiä kasvattavilla silmukoilla.
Keywords are words in programming languages that have been reserved. Good text editors generally use a different formatting for keywords (e.g. bold). Usually keywords are protected and their names cannot be used for variables. Typical keywords include if and else that are used in control structures. In a way keywords are part of the programming language's grammar.
A library is typically a toolbox of functions around a single purpose. Libraries are taken to use with the include directive. If a library is not part of the C standard library, its use must also be told to the compiler.
Logical operation refers to Boole's algebra, dealing with truth values. Typical logical operations are not, and, or which are often used in conditional statements. C also uses bitwise logical operations that work in the same way but affect each bit separately.
Machine language is made of instructions understood by the processor. Machine language is often called Assembly and it is the lowest level where it's reasonable for humans to give instructions to computers. Machine language is used at the latter part of this course - students taking the introduction part do not need to learn it.
Macro is an alias that defines a certain keyword to be replaced by a piece of code. When used well, macros can create more readable code. However, often the opposite is true. Using macros is not recommended in this course, you should just be able to recognize one when you see it.
In C the main function is the starting point when the program is run. The command line arguments of the program are passed on to the main function (although they do not have to be received), and its return value type is int. At its shortest a main function can defined as int main().
When programs are run, all their data is stored in the computer's memory. The memory consists of memory slots with an address and contents. All slots are of equal size - if an instance of data is larger, a continuous area of multiple memory slots is reserved.
Method is a function that belongs to an object, often used by the object to manipulate itself. When calling a method, the object is put before the method: values.sort().
Object is common terminology in Python. Everything in Python is treated as objects - this means that everything can be referenced by a variable (e.g. you can use a variable to refer to a function). Objects are typically used in object-oriented languages. C is not one.
Optimization means improving the performance of code, typically by reducing the time it takes to run the code or its memory usage. The most important thing to understand about opimization is that it should not be done unless it's needed. Optimization should only be considered once the code is running too slowly or doesn't fit into memory. Optimization should also not be done blindly. It's important to profile the code and only optimize the parts that are most wasteful.
A parameter is a variable defined alongside with a function. Parameters receive the values of the function's arguments when it's called. This differentation between parameters and arguments is not always used, sometimes both ends of the value transfer are called arguments.
Placeholders are used in string formatting to mark a place where a value from e.g. a variable will be placed. In Python we used curly braces to mark formatting placeholders. In C the % character is used which is followed by definitions, where the type of the value is mandatory. For instance "%c" can only receive a char type variable.
Pointers in C are special variables. A pointer contains a memory address of the memory location where the actual data value is located. In a sense they work like Python variables. A variable can be defined as a pointer by postfixing its type with * when it's being introduced, e.g. int* value_ptr; creates a pointer to an integer. The contents of the memory address can be fetched by prefixing the variable name with * (e.g. *value_ptr. On the other hand, the address of a memory adress can be fetched by prefixing a variable name with &, (e.g. &value.
The C precompiler is an apparatus that goes through all the precompiler directives in the code before the program is actually compiled. These directives include statements which add the source code of the included libraries into the program, and define directives that can define constant values (aliases) and macros.
Directives are instructions that are addressed at the precompiler. They are executed and removed from the code before the actual compilation. Directives start with the # character. The most common one is include which takes a library into use. Another common one is define, which is used e.g. to create constant values.
Prototype defines a function's signature - the type of its return value, its name and all the arguments. A prototype is separate from the actual function definition. It's just a promise that the function that matches the prototype will be found in the code file. Prototypes are introduced at the beginning of the file or in a separate header file. In common cases the prototype definition is the same as the line that actually starts the function introduction.
Interactive interpreter or Python console is a program where users can write Python code lines. It's called interactive because each code line is executed after its been fully written, and the interpreter shows the return value (if any).
The format method of string in Python is a powerful way to include variable values into printable text. The string can use placeholders to indicate where the format method's arguments are placed.
Python functions can have optional parameters that have a given default value. In Python the values of arguments in a function call are transferred to function parameters through reference, which means that the values are the same even though they may have different names. Python functions can have multiple return values.
In Python the import statement is used for bringing in modules/libraries - either built-in ones, thrid party modules or other parts of the same application. In Python the names from the imported module's namespace are accessible through the module name (e.g. math.sin). In C libraries are taken to use with include, and unlike Python import it brings the library's namespace into the program's global namespace.
Python lists were discovered to be extremely effective tools in Elementary Programming. A Python list is an ordered collection of values. Its size is dynamic (i.e. can be changed during execution) and it can include any values - even mixed types. Lists can also include other lists etc.
In Python main program is the part of code that is executed when the program is started. Usually the main program is at the end of the code file and most of the time under if __name__ == "__main__": if statement. In C there is no main program as such, code execution starts with the main function instead.
In Python a variable is a reference to a value, a connection between the variable's name in code and the actual data in memory. In Python variables have no type but their values do. The validity of a value is tested case by case when code is executed. In these ways they are different from C variables, and in truth Python variables are closer to C pointers.
Pythonin for-silmukka vastaa toiminnaltaan useimmissa kielissä olevaa foreach-silmukkaa. Se käy läpi sekvenssin -esim. listan - jäsen kerrallaan, ottaen kulloinkin käsittelyssä olevan jäsenen talteen silmukkamuuttujaan. Silmukka loppuu, kun iteroitava sekvenssi päättyy.
Pääfunktio on C:ssä ohjelman aloituspiste ja se korvaa Pythonista tutun pääohjelman. Oletuksena pääfunktion nimi on main ja se määritellään yksinkertaisimmillaan int main().
Resource referes to the processing power, memory, peripheral devices etc. that are availlable in the device. It includes all the limitations within which programs can be executed and therefore defines what is possible with program code. On a desktop PC resources are - for a programmer student - almost limitless, but on embedded devices resources are much more scarce.
Return value is what a function returns when its execution ends. In C functions can only have one return value, while in Python there can be multiple. When reading code, return value can be understood as something that replaces the function call after the function has been executed.
A statement is a generic name for a single executable set of instructions - usually one line of code.
C uses static typing This means that the type of variables is defined as they are created, and values of different types cannot be assigned to them. The validity of a value is determined by its type (usually done by the compiler). Python on the other hand uses dynamic typing aka.duck typing.
In Python all text is handled as strings and it has no type for single characters. However in C there are no strings at all - there's only character arrays. A character array can be defined like a string however, e.g. char animal[7] = "donkey"; where the number is the size of the array + 1. The +1 is neede because the string must have space for the null terminator '\0' which is automatically added to the end of the "string".
Syntax is the grammar of a programming language. If a text file does not follow the syntax of code, it cannot be executed as code, or in the case of C, it cannot be compiled.
Terminal, command line interface, command line prompt etc. are different names to the text-based interface of the operating system. In Windows you can start the command line prompt by typing md to the Run... window (Win+R). Command line is used to give text-based commands to the operating system.
The data in a computer's memory is just bits, but variables have type. Type defines how the bits in memory should be interpreted. It also defines how many bits are required to store a value of the type. Types are for instance int, float and char.
Typecast is an operation where a variable is transformed to another type. In the elementary course this was primarily done with int and float functions. In C typecast is marked a bit differently: floating = (float) integer}. It's also noteworthy that the result must be stored in a variable that is the proper type. it is not possible to change the type of an existing variable.
Unsigned integer is a an integer type where all values are interpreted as positive. Since sign bit is not needed, unsigned integers can represent twice as large numbers as signed integers of the same size. An integer can be introduced as unsigned by using the unsigend keyword, e.g. unsigned int counter;.
In the elementary programming course we used the term value to refer to all kinds of values handled by programs be it variables, statement results or anything. In short, a value is data in the computer's memory that can be referenced by variables. In C the relationship between a variable and its value is tighter as variables are strictly tied to the memory area where its value is stored.
A warning is a notification that while executing or - in this course particularly - compiling it, something suspicious was encountered. The program may still work, but parts of it may exhibit incorrect behavior. In general all warnings should be fixed to make the program stable.
One way to print stuff in C is the printf function, which closely resembles Python's print function. It is given a printable string along with values that will be formatted into the string if placeholders are used. Unlike Python, C's printf doesn't automatically add a newline at the end. Therefore adding \n at the end is usually needed.
Out of loops, while is based on repetition through checking a condition - the code block inside the loop is repeated until the loop's condition is false. The condition is defined similarly to conditional statements, e.g. while (sum < 21).