C

C is a versatile, mature and efficient language.

Expressions are a combination of operators and operands.
An expression followed by a semmicolon (“;”) is a statement (it is an action)

C concepts
Memory Management
Structs
Debug messages
Random numbers

Defines

In C you can define stuff that's quickly replaced by the preprocessor.

Let's say you have the following program:

#include <stdio.h>
int main()
{
	printf("Hello, World!\n");
#ifdef DEBUG
	printf("Secret debug info!\n");
#endif
	return 0;
}

Compile it with gcc -o prog -c prog.c -DDEBUG. Your program will print out the secret debug info in addition to its regular output.
This is useful for debugging and more.

Storage-class specifiers

Make a variable's storage class more explicit to the compiler.

static - block scope
Block-scope static variables will keep their values between function calls. They're only initialized once at program startup, unlike regular function variables.
static - file scope
File-scope static variables (outside of any function) are restricted to the current source file only. You can't access them from another source file.

Notes

Strings can be literals or arrays. Deep down, they're just pointers to the start of the char array.
However, string literals are stored read-only and cannot be modified: char* s;
If you want to make a mutable string, declare it as an array of characters: char s[];
The arrow operator (→) is used to access fields in a pointer to a struct.
For example: thinkpad->price = 800; (thinkpad is a pointer to a struct laptop thinkpad struct)
This is useful instead of writing it as (*thinkpad).price = 800;
Include <stdint.h> for fixed-size types such as uint64_t

Table of Contents

C

Defines

Storage-class specifiers

Notes

See also