C - astromechanic/cheat_sheets GitHub Wiki

File extension .c

Cloud IDE from CS50 https://ide.cs50.io/ У меня в облаке на CS50 лежит пара программ на С.

Source code .c To run a program, you need to compile the source code into binary. Only the binary file is executable

Hello World

#include<stdio.h>
int main(void)
{
    printf("Hello, world");
}
// this is a comment

Compile and run some simple stuff

gcc -o hello hello.c
./hello

gcc is a compiler collection. We can also use another one, called clang. It looks like this:

clang -o hello hello.c

When using a header is not enough to tell the computer how to execute/understand where the functions from the library come from (= it's not enough to include the header), then use -l + name of the library:

clang -o hello hello.c -lcs50

Get two numbers from the user and add them

#include<cs50.h>
#include<stdio.h>

int main(void)
{
    int x = get_int("x: ");
    int y = get_int("y: ");
    printf("%i\n", x + y);
}

Divide two numbers

#include<cs50.h>
#include<stdio.h>

int main(void)
{
    int x = get_int("x: ");
    int y = get_int("y: ");

    float z = (float) x / (float) y; // casting = convert int x into float
    printf("%f\n", z);
}

if (x > y) 
{
   // do something
}
else if (x < y)
{
   // do something else
}
else 
{
   // do something else
}

Functions

void meow(void); // prototype - in order that compile knows that there is a function meow()

int main(void)
{
    meow(3);
}

void meow(int n)
{
    for (int i = 0; i < n; i++)
    {
       printf("meow");
    }
}

Arrays

int scores[3]; // declaring an array you need to specify type and length
scores[0] = 72;
scores[1] = 43;
scores[2] = 34;
double balance[5] = {1000.0, 2.0, 3.4, 7.0, 50.0}; // init an array

Use single '' for separate chars: char c = 'H'; Use double "" for everything else: string s = "Hi";


#include<string.h>
strlen(string) // get length of string
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