C

The C programming language was devised in the early 1970s by Dennis M. Ritchie an employee from Bell Labs (AT&T). Although originally intended to write Unix kernel, it remains so popular and could be considered a father of almost all modern programming languages we see today.

Example & Compiling

# lets assume there is a file called test.c that looks like this

#include <stdio.h>

int main() {
    printf("Hello AI\n");
    return 0;
}

# we can compile this c program with gcc compiler whose syntax is like this:

SYNTAX: gcc [options] source_files -o output_file

# Compile your file test.c and create an executable output called test
gcc test.c -o test

# To run this program
./test

# Enforce C89 standard with GCC
gcc -std=c89 -pedantic test.c -o test

# Enforce C99 standard with GCC
gcc -std=c99 -pedantic test.c -o test

# Enforce C11 standard with GCC
gcc -std=c11 -pedantic test.c -o test

C Keywords

Keywords are predefined, reserved words used in programming that have special meanings to the compiler. Keywords are part of the syntax and they cannot be used as an identifier.

auto        double      int         struct
break       else        long        switch
case        enum        register    typedef
char        extern      return      union
const       float       short       unsigned
continue    for         signed      void
default     goto        sizeof      volatile
do          if          static      while

Placeholders

Placeholder	Format
`%c`	Character
`%d`	Signed decimal integer
`%i`	Signed decimal integer
`%e`	Scientific notation [e]
`%E`	Scientific notation [E]
`%f`	Decimal floating point
`%o`	Unsigned octal
`%s`	String of characters
`%u`	Unsigned decimal integer
`%x`	Unsigned hexadecimal (lower)
`%X`	Unsigned hexadecimal (upper)
`%p`	Display a pointer
`%%`	Print a %

Expression & Operators Precedence

Operator	Description	Associativity
`Function Expression`	`()`	Left to Right
`Array Expression`	`[]`	Left to Right
`Structure Operator`	`->`	Left to Right
`Structure Operator`	`.`	Left to Right
`Unary minus`	`-`	Right to Left
`Increment/Decrement`	`++, --`	Right to Left
`One’s compliment`	`~`	Right to Left
`Negation`	`!`	Right to Left
`Address of`	`&`	Right to Left
`Value of address`	`*`	Right to Left
`Type cast`	`(type)`	Right to Left
`Size in bytes`	`sizeof`	Right to Left
`Multiplication`	`*`	Left to Right
`Division`	`/`	Left to Right
`Modulus`	`%`	Left to Right
`Addition`	`+`	Left to Right
`Subtraction`	`-`	Left to Right
`Left shift`	`<<`	Left to Right
`Right shift`	`>>`	Left to Right
`Less than`	`<`	Left to Right
`Less than or equal to`	`<=`	Left to Right
`Greater than`	`>`	Left to Right
`Greater than or equal to`	`>=`	Left to Right
`Equal to`	`==`	Left to Right
`Not equal to`	`!=`	Left to Right
`Bitwise AND`	`&`	Left to Right
`Bitwise exclusive OR`	`^`	Left to Right
`Bitwise inclusive OR`	`\|`	Left to Right
`Logical AND`	`&&`	Left to Right
`Logical OR`	`\|\|`	Left to Right
`Conditional`	`?:`	Right to Left
`Assignment`	`=, *=, /=, %=, +=, -=, &=, ^=, \|=, <<=, >>=`	Right to Left
`Comma`	`,`	Right to Left