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

Variable Types in C

Learning Objectives: After going through this material, you will know the types of variables commonly used in the C language.

Variable Types

The C language standards have predefined a set of variable types for the convenience of the programmer (and okay, to save memory). The variable type tells us its intended use: character, integer, or floating-point number. Since the variable type is standardized, you can rely on it to work the same way across different development environments and systems.
Variable Type Keyword Bytes Standardized?
Character char 1 Yes
Integer (word) int 2 / 4 No, depends on the architecture. Modern architectures 4 bytes in general
Short integer short int At least 2 Yes.
Long integer long int At least 4 Yes
Single-precision floating-point float 4 Yes
Double-precision floating-point double 8 Yes
You can check the size of different types using the sizeof operator.
Bytes size of different types 
#include <stdio.h>

int main()
{
    printf ("The size of char is %zu bytes\n", sizeof(char));
    printf ("The size of short int is %zu bytes\n", sizeof(short int));
    printf ("The size of int is %zu bytes\n", sizeof(int));
    printf ("The size of long int is %zu bytes\n", sizeof(long int));
    printf ("The size of float is %zu bytes\n", sizeof(float));
    printf ("The size of double is %zu bytes\n", sizeof(double));
    return 0;

}

Integers

In the C language, integers are represented as two's complement numbers. According to the standard, integer variable types are guaranteed to have minimum and maximum ranges, meaning the variable will work within this specified range regardless of the compiler and computer. (Note! The full range is not always available as specified in the standard.)
"The standard is your friend"
The integer variable type can be refined with qualifiers:
For example, a 4-bit integer's range: unsigned and signed.
"signed vs unsigned"

Character Variable

The character variable char is an interesting type because, in the C language, it is actually at least an 8-bit number, whose value is interpreted by the compiler as a character according to the ASCII table. So, every character corresponds to a numeric value in the C language. This solution is inherited from the 1970s when handling characters separately would have been too expensive and memory-intensive.
This leads to interesting results. If the programmer wants, they can forget the character nature of the char type and use it (as a signed integer) for integer variables. This allows for arithmetic operations on letters to work, as they are interpreted by the compiler as numbers. Only when character is shown in any system output the corresponding character is presented. For example, operations like 'a' + 1 = 'b' (97 + 1 = 98) or 'c' - 'a' = 2 (99 - 97 = 2).
In embedded programming, this is actually hugely beneficial in resource-constrained devices, as strings composed of letters can be handled numerically, such as comparing the "equality" of two words. Strange but handy.
Please, note that in moder system, instead of ASCII we are using Unicode symbols which allows to present larger set of characters in different languages (e.g. cyrilic ...). In this case, most popular encoding is UTF-8(4 bytes). Recent C standards like C11 supports already unicode, but we are not going to cover that much about it in this course.

Other variable modifiers

C also has register, pointer, global, and static variables, but more on those later.

Derived Types

The C language standard defines a set of derived variable types. From now on in this course, we will use these variable types to keep the size of the used variable clear in our program code.
Derived Variable Type Size in Bytes
int8_t / uint8_t 1
int16_t / uint16_t 2
int32_t / uint32_t 4
int64_t / uint64_t 8
The intN_t variable type means a signed integer, and the uintN_t type means an unsigned integer. The use of fixed-width types is increasingly important in modern programming specially in cross-platform development. These types are also widely use in C++ and are critical to ensure portability across different systems.
Only available from the C99 standard. You need to use the <stdint.h> library. This is the preferred way of defining variables (specially ints) in this course, specially when we move to the embedded programming part.

Initializing Variables

Initializing variables, as in many other programming languages, happens when the variable is assigned its value (value that is stored in memory). This process is usually done at the same time as the variable definition.
Examples of initializing integer variables:
int16_t integer = -123;
uint16_t unsigned_integer = 3333;

uint32_t long_integer = 0x12345678;

double floating_point = 1.234;
float smaller_floating_point = 1.2e-10;
For character variables char, the initialization uses the ' (single quote) to enclose a character, or a number as shown above. The corresponding ASCII value is stored in memory.
These initializations are equivalent:
char character = 'a'; // Value is the ASCII code for 'a'
char character = 97;  // In the ASCII table, 'a' corresponds to the number 97

Challenges

Since C is an old hardware-oriented programming language, many things are left to the programmer's knowledge.
For example, if a programmer tries to initialize a variable with a number outside its range, the C compiler politely generally (depends on the compiler, and the used flags) warns of an error .
int8_t a = 1234;
...
warning: overflow in implicit constant conversion.
OFFTOPIC: If you want to be sure that compiler warns about this possible error (and many others) you can compile it with the -Wall flag.
However! The compiler only warns about the error, and the program continues to compile. It's important to be careful not to let such mistakes end up in the compiled program.
What happens in the compiler?why is this just a warning? We know that a specific amount of memory, based on the type, was allocated for the variable (int8_t is one byte). Now, if more data is written into the variable than it can hold, a memory overflow occurs. Fortunately, C compilers catch this. However, the solution is quite brutal, as the compiler simply chops off the extra bits of the number, like a guillotine.
OFFTOPIC:
What is the difference between warning vs error?

WARNING: A warning is a message generated by the compiler that indicates a potential issue in the code. The compiler allows the program to compile and run, but it alerts the developer to something that could lead to unintended behavior or a bug. Warnings do not stop the compilation process, but they highlight areas of code that may need attention.

ERROR: An error is a message from the compiler that indicates a critical issue in the code, which prevents the program from being compiled. Errors usually indicate syntax or semantic mistakes that must be corrected before the code can be successfully compiled and executed.
In the example above, here's what happens: 1234 in binary is 10011010010 (11 bits). The compiler cuts off the top three bits 100, so that the remaining 8 bits fit in memory 11010010. The problem is that this binary number is interpreted as a two's complement number, so the variable a is initialized as int8_t a = -46 instead of the intended 1234. Oops!!!!

Array Variables

In C, array variables are declared using square brackets (as in many other programming languages), with the size of the array inside the brackets. You can declare arrays for all basic variable types (and other types, which we'll cover later). Of course, multidimensional arrays are also possible in C.
The syntax is as follows:
uint8_t array[5];
uint8_t array[5] = { 1, -3, 5, -7, 9 }; // Initialize at the same time
uint8_t array[] = { 1, -3, 5, -7, 9 }; // Compiler determines the array size automatically! 
//This is wrong: uint8_t[]; We cannot define an array without including its size unless we are initializing at the same time. 
uint8_t array[3][3]; 
uint8_t array[2][3] = { { 1, 2, 3 }, // Initialize
                        { 4, 5, 6 }, 
                      };						
uint8_t array[][3] = { { 1, 2, 3 },  // The compiler can sometimes determine the array size!
                       { 4, 5, 6 }, 
                       { 7, 8, 9 } };

Strings

Since C does not have a separate string variable type, strings are arrays of type char. That is, they are regular numeric arrays, but the compiler interprets them as representing characters according to the ASCII table.
However, there is a little elegant peculiarity in initializing strings. Strings must always end with the literal character '\0' (NULL Terminator). This is crucial to know because many C standard library functions (and other ready-made functions) assume this! String handling in the program typically breaks if the string does not end with a zero. See for instance how strlen and strcpy uses the null terminator to detect the end of a string. Forgetting the null terminator, will lead to security vulnerabilities, such as buffer overflow.
Note! The null terminator is entirely different (in the compiler's view) from the ASCII character '0', which corresponds to the number 48. Null terminator is represented in memory by 0x00.
String initialization can be done in several ways, just like with arrays, as shown above.
char message[] = "Hello"; // The compiler automatically adds a trailing 0, array length is 5+1 characters
char message[6] = {'H', 'e', 'l', 'l', 'o', '\0'};
char message[] = {'H', 'e', 'l', 'l', 'o', '\0'}; // The compiler calculates the array size
char message[] = {72, 101, 108, 108, 111, 0}; // ASCII codes for the characters
If we initialize a string/array too short, the compiler will automatically fill it with zeros. The following initializations are equivalent:
char message[5] = "H";
char message[5] = {'H'};
char message[5] = {'H', 0, 0, 0, 0 };

Indexes

Otherwise, handling arrays is familiar: you move through them using indexes, as in other programming languages. However, the first index value is 0 and the last allowed index is array size - 1.
An example of using indexes:
uint8_t array[3][3] = { { 1, 2, 3 }, 
                        { 4, 5, 6 }, 
                        { 7, 8, 9 } };

for (i = 0; i < 3; i++) {     // elements 0,1,2
    for (j = 0; j < 3; j++) { // elements 0,1,2
        printf("%d\n", array[i][j]);
    }        
}
You can also traverse arrays in other ways, which we will cover in upcoming material on pointers. Being close to the hardware offers all kinds of fun ways to handle memory. In some cases, a skilled or even less skilled programmer might manage to go outside the bounds of an array using an index, without the compiler noticing, so be careful!! This can lead to situations named as undefined behaviour an important concept in C. Sometimes applications might work, other time might crash.

Variable Type Conversions

In C, the type of variables can be changed according to certain rules. The standard explains this in detail, but the following general rules are sufficient for us.
Examples.
uint8_t a = 1234; // Compilation produces an error message
main.c: In function 'main':
main.c:6: warning: large integer implicitly truncated to unsigned type

// Addition where the result wraps around the value range
// The maximum value for int8_t is 127
int8_t a = 33;
int8_t b = 101;
int8_t c = a + b // result is -122

Forcing Type Conversion (Casting)

C provides a type conversion operator (known as a cast), which can be used to force a conversion at any point in the code. This can be useful when, for example, a library function requires arguments of a specific type. The cast operator is in the form (typename) expression.
Example.
uint16_t x = 7;
double y = sqrt((double) x); // Here, x is forced to double 
// before calculating the square root
The cast operator can break the previously mentioned hierarchy when needed.

Fahrenheit to Celsius converter

We want to build a Fahrenheit to Celsius Converter. You can find many of them in Internet.
The formula is:
5/9 * (Fahrenheit - 32)
We wrote the following C code to implement the converter. But there is something wrong...
Fahrenheit to Celsius tranformer 
#include <stdio.h>
int main()
{
    int c1= 5;
    int c2 = 9; 
	int c3 = 32;
    float fah = 212.0;
    float cent = c1/c2*(fah-c3);
    printf ("%.2f Fahrenheit are %.2f Centigrades",fah, cent);
    return 0;
}
If you try to calculate 212 Fahrenheit in Celsius, write: * The expected result in the first line * The obtained result in the second line
Warning: You have not logged in. You cannot answer.

Conclusion

We will work more with arrays in conjunction with pointer variables. When dealing with variable conversions and initializations, it is good to remember the compiler's guillotine, which can save you from many strange bugs.
?
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).