# Lovelace

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
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

# 1. The a, b, ... ( •_•)>⌐■-■ ...C of this course¶

On this page you will take the first steps away from the familiar Python of the Elementary Programming course and towards a new conquest: the marvelous programming language C. At the same time you get to know a bit more about the course and its relationship with the Introduction to Programming and, of course, about C as a tool.

## Learning objectives¶

This time you learn what C has to do with this course and why it has been considered necessary to switch the language. The key learning points are the principle differences of these languages that strongly affect the way of programming with them. In addition you will learn the first differences between the
syntaxes
of them.

## C programming on this course¶

Before we get to comparing these two languages, it is crucial to tell you a bit more about the relationship of this course, programming, and C.

### This is not an elementary course of programming¶

For starters, this course continues from where the Elementary Programming course left off. We assume that you know the very basics of programming and we do not have to teach you them again. There is some material that should refresh your memories about Python so that through the language can be shown some of the differences between Python and C. If some things feel completely alien, it is likely you can understand them better if you check the Elementary Programming course material. The order of the contents of the course is about the same as it was in Elementary Programming, but they focus on how to do the things in C instead of Python.

### This is not a C programming course¶

Another important thing to note about this course is that C is only a tool to get to the core of the course. The language is taught from the point of view of embedded systems programming. On the course there are several things about C language that are relevant mostly when you are programming large software for computers. Some standards of the C language are mentioned in the material when it is useful for the course.

### This is an embedded systems programming course¶

This course is a combination of two old courses: Embedded Systems Programming and Computer Engineering - although only the ones doing the 8 credits version find out things related to the latter. This part you are currently reading is included in the 5 credits part and thus is completely about the topics of the former Embedded Systems Programming course. On the lectures you can learn more elaborately about embedded systems, but as a short summary: this course goes much deeper than the Elementary Programming course and is focused on small devices with limited processing power and memory (naturally regular computers also are limited in the same way, but they usually are not so limited that you have to worry about that nearly as much). C offers tools for better
resource
allocation and lets us directly prod the computer's
memory
and low level processes.
What this more accurate control of the processes and memory means you will find out bit by bit as you proceed through the course material. At this point is relevant to remember that the more precise control a tool offers the more precise work you have to do yourself to use it.

## From Python to C¶

In this portion is introduced some of the basic differences of the languages. You do not yet need to perfectly understand what these differences mean in practice, but from the start it is good to know they exist. It is also good to know that even if the differences may sound like just semantics, for the most part they - especially in embedded systems programming - have a huge impact on how to write the programs. These differences also hopefully demonstrate the reasons why Python was chosen as the elementary programming language and was now switched to C for this course. In short, Python has lots of automation that eases programming so that it is not that necessary to handle all the small details. However, the efficiency (which does not matter as much at it used to with modern computers) and the fine control(which you don't usually need with programming) suffer because of the automation.

### Compiled language vs interpreted language¶

On the Elementary Programming course you may have run into Python
interpreter
, a program that runs Python code. On this course we will not be talking about interpreters much, because C is not interpreted, it is
compiled
. Whatever the programming language, the code will end up in a
machine language
format. Machine language consists of simple
instructions
for the processor. These instructions may seem very limited to humans, but humans have programmed using it - and still are programming using it, and the students taking part in the later part of the course will get to enjoy it. In practice, programming languages are
abstractions
that have been built on machine language and they offer a more human-friendly collection of commands. Both compiling and interpreting are processes that turn the programming language into machine language for the processor. The name choices are not random - their analog counterparts picture well the differences between the processes. Like in real life when a language is "compiled" the whole text is processed after which the
compiler
sends the finished output forward. "Interpreting" on the other hand happens in real time, the sentences are interpreted one by one.
The nature of interpreting manifests well while using Python's
interactive interpreter
; you can get every written line's output right away:
>>> 5 + 5
10
>>>

Another clear manifestation of it is how Python program often runs up to some point after which it crashes - it only works partly. Especially from the point of view of a beginner this is useful, because this way it is easy to examine how the faulty program acts. However, as a drawback of interpreting is that, because the machine language is produced on the fly, it uses resources while it runs. Another drawback is that while interpreting it has to be taken into account that the next line of code can be anything, which also eats up resources. On a test run this extremely simple Python program used 8 MB of
memory
:
input(": ")

A couple of decades ago 8 MB would have been the size of the whole RAM of a computer. Almost all of this goes in Python's own usage - the upkeep of the architecture that interprets code. As a proof of this the example minesweeper does not take any more memory than that. Python's processing power can be
optimized
with different tools (e.g. PyPy), but that is not very relevant to this course.
Life with a
compiler
is quite different. With it executing the program has two steps: in the first step the code is run through the compiler and it outputs a
binary code file
, which contains the actual executable program. The compiling is done only once. While executing the program it is already in a form that can be given straight for the processor. During the executing resources are not used for compiling at all. Also during the execution there will be less surprises, since the compiler has gone through the whole code. Compilers typically do some optimization - after going through the whole code they can choose the best way to execute the logic. This is possible just because the whole code is known before execution. The C equivalent of the Python example above used up only 640kB of memory. We may look at the code of that program later.
Looking for and solving bugs with a compiler is substantively different. Usually a faulty code can not be executed at all, because it is rejected in the compiling phase. The error and the way it can be fixed has to be read from the
error message
. Even if the program compiles it can also crash also while executing. In addition to error messages, the compiler outputs
warnings
of potential problems. Typically also these are good to fix before executing the program, but even that does not guarantee the program will work. In the end you also have to test the code after compiling anyway. Because of that, there is an additional work step of compiling the code after each change made to the code. If the program is large compilation of several parts, the compilation can take a notable time. At this point one thing you can be sure of: you get to familiarise yourself with all of this many times during the course.

### Static vs dynamic type¶

Regarding many new things Python is rather open. As we (hopefully) remember, the typical way of handling
exceptions
is "try first, regret later." The way Python manages variables is quite liberal. In most situations the type of a variable is not checked - instead it is only tested whether or not the value of the
variable
happens to work in the current situation. This is
dynamic typing
, which is also known as duck typing - if an animal walks like a duck, swims like a duck, and talks like a duck, it can be considered a duck whether or not it really is a duck. If we have, for example, a mathematical
function
, it is only interested in can it compute using the given arguments, not what type the numbers are. The most exact ones may still remember that Python's variables do not even have a type, only their values do. You can set a string to a variable at some point, and a list at another:
>>> aline = "aasi,svengaa,5,10.0"
>>> aline = aline.split(",")

C, on the other hand, has
static typing
. It means that all the types of all variables have to be defined in the code separately. This also applies to the
parameters
and
return
values of functions. The compiler ensures a round piece will not be pushed in a triangular hole even if it was small enough to fit. If the type of the variable has to be changed on the fly, it has to be written in the code separately or the operation will be illegal. With normal variables this difference is not as relevant as the previous one, because the usage of variables is only a little bit more tedious and requires only a bit more work. There are programmers who are vehemently of the opinion that this kind of more strict typing is best and they have theri reasons: it prevents certain mystical errors that appear when something is thought of as a duck and later is revealed to be a goose instead (in other words, the variable had only some of the required attributes, for example a string works in some situations like a list, but not in all). Below you can see a couple of examples of defining variables with type in C:
int jalkojen_lkm = 4;
float korvien_vali = 30.15;

Unfortunately things get more complicated when we move from simple data types to
structures
. The handy general tool of Python,
list[!list!], does not exist in C. C does have its own structure for putting a handful of values in a line. This structure is called [!term=Array!]array
. Array happens to be more unwieldly than list. For arrays you have to define in its
introduction
how many elements it can contain and what type they are - the length of an array can not change during the execution of the program, and it is not possible to put different types of items in it. Naturally it is possible to come up with solutions to this, but they are not easy, and usually they do not reach the level of versatility of the lists of Python. Fortunately you will not need them much on this course.
There is one more difference between the typings: on the Python course you may have been constantly reminded that
variables
do not contain values, they only point at them. All the variables worked in the same way. But in C there are
variables
that contain values and variables that contain
pointers
to values. This separation is one of the most difficult things to learn about C programming, because it can cause very mystical errors when the memory is accessed without doing it through variables. This is why we have on this course material a part dedicated for this problem.

### Syntax differences¶

Perhaps the most insignificant difference between the languages, at least in terms of problem solving, is that they look a bit different. Let us begin from the easiest one: in C the
statements
, usually individual lines of code, end with a semicolon, while in Python they simply end at the end of the line. A compiler can point out missing semicolons rather eagerly. Another difference is related to marking up [!term=Block of statements]blocks of statements[!term!]. In Python the blocks are separated by indentation. In C the indentation does not matter and the blocks are marked with curly braces - everything within a pair of curly braces belong to the same block of statements. Naturally there can be more blocks within a block also. Curly brackets are used with
functions
and
control structures
. Even when the indentation does not mean anything, using indentation like in Python makes the code significantly easier to read with human eyes. Other very small differences are, among others, that conditionals and things resembling them are put between parentheses and some symbols are used differently.
In C the
main program
does not exist the same way as in Python either. Instead of it in C there is the
main function
, from which the execution of the program begins. Because of this, in a simple C program there is more stuff:
#include <stdio.h>

int main() {
printf("aasisvengaa!\n");
return 0;
}

Equivalent in Python:
print("aasisvengaa")

In the example you can see a couple of other differences also. #include <stdio.h> works the same way as Python's import. It is required for using printf function, since you need to get it from stdio-
library
(standard input/output). int main() is a definition of the main function. A separate
keyword
, like def in Python, does not exist in C for marking a function. A function is recognized by parentheses at the end of its name, otherwise its introduction looks similar to a variable's introduction, since you have to define the function's return value's type when you introduce the function.

## C tools¶

Before diving deeper, at the end of this introduction page is some basics of executing a C-program. Like was mentioned before, compared to "starting" a Python program there is one additional step with C: compiling. As a tool we use a
C compiler
, which should have been installed by now. In this material the compiler and programs are executed in
terminal
, like with Elementary Programming course. As an example we could use the code above. In terminal you navigate to the directory where the code is located. After that you cast this basic spell (in Windows):
C:\path\to\somewhere>gcc -Wall -o svengaa.exe svengaa.c

In this line "gcc" is the name of the compiler. The rest are its commandline parameters, of which the last one is the name of the source code file. The third and fourth, -o svengaa.exe, belong together: -o says that the next parameter will be the name of the compiled program. In linux the spell is the same otherwise, but .exe is left out - Linux executables usually do not have endings like that. After this the program can be executed:
C:\path\to\somewhere>svengaa.exe
aasisvengaa!

A compiler is a quite complicated thing and -o is only one of the todella many of its
flags
. On this course we will not touch the inner workings of a compiler very much, but some other flags probably will be used.

## Summary¶

This time we went through C language on a very general manner. We took note of some principle differences between it and Python. Basically we prepared for the future, and the meanings of these differences will come clearer when we get to details. In any case, at the beginning is good to be aware of how C is not an animal like Python; it won't be a huge surprise that things have to be done in somewhat different ways. In C programming the coder has to handle more details. But as a reward they get more superpowers for controlling the lives of computers.
?
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).