C-cheatsheet.md

C Cheatsheet

Comments

// This is a single-line comment
/*
    This is a multiline comment
*/

Variables

Integer number types

short a = -4;
ushort b = 1;
int c = -0;
uint d = 1;
long e = 4L; // = 4l;
unsigned long f = 7UL; // = 7ul = 7uL = 7Ul;
long long g = -9LL; // = -9ll
unsigned long long h = 9ULL; // = 9ull = 9uLL = 9Ull;

Floating-point number types

float x = 9.5f;
double y = 9.5;

Enum types

enum enum_name {e_val0, e_val1, e_val2, e_val3 = 10, e_val4, e_val5 = -1, e_val6};
enum enum_name enum_instance;
enum_instance = e_val9; // 0
enum_instance = e_val1; // 1
enum_instance = e_val4; // 11
enum_instance = e_val6; // 0

Character types

char c = 'c'
c = '9'
c = 35; // '#', see ASCII table
unsigned char t = '9'

Boolean types

TODO

Array types

// Creation
int int_storage[8]

Character strings

// String of 19 characters, v[19] is '\0'
char v[20]
// Initialized string, automatically adds '\0' at the end
char word[] = {'N','o','t',' ','f','u','n','n','y'}
char word2[] = {"Way better!"}
// If explicit size, account for '\0'
char word3[7] = {"Hello!"}

#include <string.h>
char src[50] = {"La donna e mobile"}
char dest[50]

Operators

Arithmetic operators

int x;
x = 4 + 2; // 6
x = 4 - 2; // 2
x = 4 * 2; // 8
x = 4 / 2; // 2
x = 7 % 3; // 1
x++ = 1;   // 2
x-- = 7;   // 6

Logical operators

_Bool a = 0;
_Bool b = 1;
_Bool c;
c = a && b; // 0
c = a || b; // 1
c = !a ^ b; // 0
c = !a; // 1

Assignment operators

int a = 8;
int b = 7;
int c;
c = a; // 8
c += b; // 15
c -= a; // 7
c *= -b; // -56
// See more in guide

Relational operators

int x = 8;
int y = 9;
x == y; // False
x != y; // True
x > y;  // True
x >= y; // True
x < y;  // False
x <= y; // False

Control flow

Conditional execution - if - else

int a = 1;
// Single-line if
if (a > 1)
    printf("Hello, smaller");

// Multiline if
if (a == 1){
    ++a;
    printf("Now it is bigger!");
}

// Single-line if-else
if (a > 1)
    printf("Hello, smaller");
else
    printf("It turnt nigger over time");

// Multiline multi-condition if-else
if (a == 1){
    ++a;
    printf("Now it is not bigger!");
} 
else if (a == 2){
    printf("This is the end");
} 
else {
    printf("Stop it");
}

Ternary operator - ?:

int a = 9;
int b = 0;
(a > 8) ? (a += b) : (b += a);

Selector - switch - case

int a = 9;
switch (a){
    case 7:
        printf("7");
        break;
    case 8:
        printf("8");
        break;
    case 9:
        printf("9");
        break;
    default:
        printf("Default");
}

Redirection - goto

// Don't use this
comehere : printf("Tak");
int a = 8;
a *= 9;
if (a < 27>)
    goto comehere;

Repeated execution - for and while

int z = 0;
for (int i = 1, j = 2; i+j < 10; i *= 2, j -= 2){
    printf("\nHi, I just wanna say \"Hello!\" for the %d time", i+j);
}
while (z > -5){
    printf("z = %d\n", z);
    z--;
}
do{
    printf("z = %d\n", z);
    z++;
} while (z < 10)

Preprocessor directives

include: include libraries

// Preprocessor directives begin by hash/pond sign
# include <stdio.h>  // Angular brackets to look for the file in standard system directories
# include "mylib.h"  // Apostrophes to look first in the current directory

define: define constants

// TAXRATE will be substituted at compile time everywhere by this value
#define TAXRATE 0.015

ifndef: avoid code duplication if already defined

Input/Output

Command-line arguments

int main(){
    // Program logic here
}

int main(int rgc, char *argv[]){
    // Program logic with command-line arguments here
}

printf (output)

printf("Here the message with %s param %d holders", var_param1, var_param2, etc);

scanf (input)

int i
char str[100]
scanf("%d %s", &i, str)