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

A typical computer

Learning Objectives: After going through this material, you will understand what is meant by the high-level architecture and organization of a computer, as well as the general principle of how a computer operates.
A computer is a general-purpose device that processes numerical-logical information according to its instructions (i.e., a program). General-purpose means that the computer can be programmed to perform various tasks. A program consists of a set of instructions presented in a language understood by the processors (i.e., machine code).
The basic operation of a computer is as follows: The processor (CPU) receives instructions and the necessary data from the computer's memory, executes the instructions on the given data, returns the results to memory, fetches the next instruction, and executes it, and so on. In essence, the computer simply repeats this cycle until the program ends or the power is turned off. According to this definition, a computer only needs a processor and memory to function.

Computer Organization

However, when components and peripherals such as a keyboard and display are added to the computer, the human and the surrounding world can interact with the computer. The term computer system describes the implementation of the computer's organization, i.e., the interconnection of the processor, memory, and peripherals into a functional computer. Peripherals are connected via buses (a set of electrical wires), allowing data transfer and operation control between different components of the system.
The image below shows a general high-level organization of a computer system.
"Basic components of a computer"

Processor / CPU

Logically, the computer's processor (also known as CPU, Central Processing Unit) is divided into two parts:
"Computer Processor"
The processor operates as follows (following the general principle of computer operation):
  1. The control unit fetches the machine code instructions to be executed and the necessary data from main memory (via bus control).
  2. The fetched instructions are interpreted to determine the operation to be performed, and the control unit places the data into the processor's small internal memory (registers).
  3. The control unit sets the processor (and its peripheral components) to a state where the operation can be performed in the ALU on the data in the registers.
  4. The ALU executes the instruction.
  5. The control unit writes the results of the instruction back to the registers, from where they are returned to main memory (via bus control).
An individual machine code instruction typically performs very simple tasks, such as a single operation, for example, an addition add A,B, which means add the values of registers A and B and store the result in register A. Since the processor only understands its own machine code at the bit level, every program written in a higher-level language (such as C) must first be compiled into machine code using a separate compiler program. As you can imagine, implementing a single high-level language command (e.g., a for-loop) might require hundreds of lines of machine code, and programs easily contain thousands of lines of machine code.
We will revisit the operation of the processor and optimization of efficiency in more detail during the Computer Systems part of the course, for those students who continue with the 8 ECTS program.

Architecture

Computer architecture describes how the organization of a computer is realized in a way that is visible to the programmer. This includes decisions such as how data is represented to the processor, what machine code instructions are available, how they are represented at the bit level, how memory appears to the program, how internal processor systems are used, how peripherals are connected, and so on. In this course, we will touch on the architecture of embedded systems to understand the challenges of memory usage in resource-constrained devices and the connections to peripherals (such as sensors).
For example, take a look at page 9 of this PDF file for the architecture of Arduino UNO R3 chip.

Word Length

As part of the processor's architecture, the size of the default data element it handles is defined. The computer can only process bits as binary numbers (more on this shortly), so the processor is assigned a word length, which indicates the largest data element the processor can handle at one time with a single machine code instruction. The larger the word size, the more and more complex data (= larger binary numbers) the processor can process at once.
For example, when an architecture is said to be 8-bit, it means that the word length is 8 bits, and thus each data element is represented to the processor as an 8-bit binary number (e.g., 10101101). Similarly, if the architecture is 16-bit, the processor can handle 16-bit binary numbers.
To handle more complex data (and to increase computing power), processor architectures are continually growing toward larger word lengths; for example, modern PCs already have 64-bit architectures. In embedded systems, 8-bit processor architectures are still seen, such as the ATmel 8-bit microcontroller in Arduino. However, nowadays, embedded systems processors are increasingly 32-bit, and even to 64 in smartphones and modern ARM MCU. The processor of both SensorTag and Raspberry Pi Pico, used in this course, is 32-bit.

System Bus

The system bus connects the CPU to external components (such as memory). Broadly speaking, the system bus can be divided into a memory bus and an I/O bus, but these solutions vary depending on the processor and computer system.
The bus is conceptualized (and implemented) as a set of parallel electrical wires to which the devices on the bus are connected.
"Basic components of a computer"
Generally, three types of electrical signals (bits, each within its own wire/s) travel along the bus: address, data, and control.
"Memory bus"
The address bus indicates the address of the data transfer destination, e.g., a memory address in main memory. The address is necessary to identify the desired data element and allocate space for it in memory where its value is stored. A memory address is simply a number (like a street address) where the desired data is stored. For example, a 16-bit number can be stored at house number 3, and it can later be retrieved for use in the program.
The address itself is formed by interpreting the voltage on the electrical conductors as bits (either 0 or 1). Each wire in the bus carries the value of one bit. All wires together, carries a binary number limited by the bus's width. If the bus has 16 conductors, a 16-bit binary number can be used as an address.
Example: When the address bus width is 16 bits, 
there are 2^16 = 65536 memory locations, i.e., memory addresses 0-65535.
In a computer, the first memory address is always 0.

In the image above, the memory location address obtained from the bits of the address bus 
is the binary number 0011000111110110, which is the decimal number 12790.
The data bus carries data bidirectionally, meaning either from the processor to memory or from memory to the processor. Similarly, the number of parallel lines on the data bus, i.e., its width, reflects the word length. Now, the entire data element can be fetched to the processor at once. In an 8-bit architecture, the data bus has 8 parallel lines, and in a 32-bit architecture, the data bus has 32 lines. (Okay, there are also solutions for fetching data elements larger than the bus width, but here we present the basic idea.)
Now in the image above, the bits of the 8-bit data bus are interpreted as the binary number 
11010110, which is -42 in decimal. (More on interpreting binary numbers in the next lecture..)
The control bus signals control the operation of the processor and peripherals (via the bus). For example, they tell the memory whether a read or write operation is being performed or activate the selected digital circuit/peripheral. Peripherals can also send control signals to the processor/control unit to indicate an operation requiring attention, e.g., a key press by the user.
Example: In the image, the control bus width is 3 bits, so it can have either 3 operations 
or 2^3 = 8 operations, depending on how the bus interpretation is implemented.

Traditionally, it can be thought that one conductor performs one function, for example, 
indicating whether a memory read or write operation is taking place, as shown in the image.

Memories

In modern computer systems, multiple types of memory are used to optimize performance, and various solutions are available for organizing memory. The goal, of course, is to make data transfer between memory and the processor as quickly as possible.
Typically, memories are organized into a hierarchy, as shown in the image below. The higher up in the hierarchy, the smaller, faster, and more expensive (per bit) the memory is. When data is written to or read from memory, data elements pass through the hierarchy:
"Memory Hierarchy"

Working Memory

Working memory (Random access memory, RAM) serves as the primary storage for instructions and processed data and is connected to the processor through the fastest possible memory bus.
The control unit of the processor interacts with the memory as follows. The control unit places the parallel bits corresponding to the memory location address on the address lines and signals whether the operation is a read or write operation. In a read operation, the memory's own control unit retrieves the data from the specified memory location and places the data element as a binary number on the data bus, from where the processor's control unit synchronously reads it and stores it in the processor's register. In a write operation, the processor's control unit places the data element from the register as a binary number on the data bus, from where the memory control unit reads it and stores it in the specified memory location.
"Writing to Memory"

Caches

The idea of a cache is to store data that the processor might need next. Naturally, it is advantageous/fast to store such data as close to the processor as possible, where it would be quickly accessible. There is usually a limited number of registers in the processor, so the cache provides a larger memory area closer to the processor.
Now, when the control unit fetches data from the main memory (as described above), the data element passes through the memory bus and is cached in various caches. In fact, with a single memory access to the main memory, it is advantageous to fetch a larger memory block (several adjacent memory locations) rather than just a single data element. This operation can be negotiated between the memory control units. As a result, when the processor needs the next instruction and/or data, they are already waiting in the cache, and there is no need to access (the slower) main memory.
Optimal utilization of the cache is an art in itself, based on algorithms implemented in the control unit that try to predict what data the program will need next from main memory. This topic will be revisited in the computer systems portion of the course.

Virtual Memory

In modern workstations, programs are offered their own memory area, called virtual memory, which consists of separate physical memories connected to the computer system, such as main memory and mass storage. For the program, this memory, made up of separate physical memories, appears as a unified memory area, thanks to the cooperation of the control units.
The idea of virtual memory is that, on the one hand, programs can be provided with memory areas larger than the main memory by including mass storage, and on the other hand, main memory can be shared between simultaneously running programs by using mass storage as a (larger) data repository.

I/O Bus

The I/O bus connects the processor to its environment, i.e., to the computer's peripherals. Typical I/O devices connected to the bus include:
The different buses in a computer are connected to each other through I/O bridges. Depending on the bus implementations, the bus widths may vary and they may have different data transfer speeds (e.g., the system bus is very fast compared to other buses), and peripherals may have different word widths. Here, the bridges create logical and physical connections between buses implemented with different technologies, using adapters. An I/O bridge, for example, can buffer data in a manner similar to a cache.
Example: In more complex embedded systems, peripheral components and devices 
may have different architectures from the processor. For example, the processor 
might be 32-bit, but the peripheral device might be 8-bit, 
such as a temperature sensor.
Communication through the I/O bus is significantly slower than with main memory. The processor communicates with devices through the I/O bus in two different ways:
The latter, interrupt-based method is generally better for program execution, as it allows the processor to do other things rather than just checking in with slow peripherals through the I/O bus and waiting for a response. In embedded systems, both methods are commonly used, depending largely on how the peripherals and components are implemented. Polling is often a cheaper way to implement electronic components, such as various sensors, because the control logic for sending an interrupt is not needed in the sensor.
Example: In the image below, an interrupt from a key press on a PC keyboard is sent to the processor, during which the pressed key's code is stored in the keyboard driver's memory and, with the help of various memory control units, is written directly to a designated memory location in main memory. The processor then responds to the interrupt signal sent by the keyboard controller and reads the pressed key's code from main memory. Therefore, the processor doesn't directly interact with the peripherals but operates with main memory.
"Interrupt"

Conclusion

The development of information technology has been so rapid in recent decades that even predictions from well-known technology leaders haven't always hit the mark...
I think there is a world market for maybe five computers.
- Thomas Watson, chairman of IBM, 1943
There is no reason anyone would want a computer in their home.
- Ken Olsen, chairman of Digital Equipment Corporation (DEC), 1977
We will delve deeper into the operation of the processor and the computer system in the computer engineering portion of the course.
?
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).