Essential C Programming Syntax and Memory Management

Posted by Anonymous and classified in Computers

Written on March 7, 2026 in English with a size of 62.93 KB

Operators

Arithmetic: +, -, *, /, %
Relation: ==, !=, >, <, >=, <=
Logic: &&, ||, !
Assignment: =, +=, -=, *=, /=, ?=
Increment: ++, --
Order of operations: (), *, /, %, +, -, <>, ==, !=

ASCII Conversions

Lowercase to uppercase: 'x' - 32
Uppercase to lowercase: 'x' + 32

Data Types

Data Types	Example	Size	Format
int	int age = 19;	4 bytes	%d
float	float a = 3.7;	4 bytes	%f
double	double pi = 3.1415;	8 bytes	%lf
char	char grader = 'a';	1 byte	%c
string	char name[20] = "pierre";	array	%s

Constants

#define TAX 0.13
const int Max = 100;

Control Structures

Statements: if, else if, else

Switches

switch(x) {
    case 1: printf("One"); break;
    case 2: printf("Two"); break;
    default: printf("Other");
}

Loops: while, do while, for

For Loop Example

#include <stdio.h>
int main() {
    for (int i = 1; i <= 5; i++) {
        printf("Value of i: %d\n", i);
    }
    return 0;
}

Functions

#include <stdio.h>
int add(int a, int b) {
    return a + b;
}
int main() {
    int result = add(7, 3);
    printf("Result: %d\n", result);
    return 0;
}

C Strings Basics

Strings are arrays of characters ending with \0.
Include library: #include <string.h>

Common Functions

Function	Purpose	Example
`strlen(str)`	Get length of string	`strlen("Hello") → 5`
`strcpy(dest, src)`	Copy string	`strcpy(dest, src)`
`strcat(dest, src)`	Concatenate strings	`strcat(str1, str2)`
`strcmp(str1, str2)`	Compare strings	`strcmp("a","b") → <0`
`strchr(str, char)`	Find character	`strchr("Hello",'e') → pointer`
`strstr(str, substr)`	Find substring	`strstr("Hello World","World")`
`sprintf(str, format, ...)`	Write formatted string	`sprintf(str,"Num=%d",x)`
`atoi(str) / atof(str)`	Convert string → int/float	`atoi("123") → 123`

Array Operations

Find the highest element

int numbers[5] = {10, 45, 30, 22, 50};
int max = numbers[0];
for (int i = 1; i < 5; i++) {
    if (numbers[i] > max) max = numbers[i];
}

Remove numbers from char array

void remNums(char a_orig[]) {
    int j = 0;
    for (int i = 0; a_orig[i] != '\0'; i++) {
        if (a_orig[i] < '0' || a_orig[i] > '9') {
            a_orig[j++] = a_orig[i];
        }
    }
    a_orig[j] = '\0';
}

Memory Management

Dynamic array with malloc

int *ptr = (int*)malloc(sizeof(int));
*ptr = 42;
free(ptr);

Pointers

& = address of variable
* = dereference (access value at pointer)
p++ moves to next memory address based on type size.

Assertions

assert(condition);

True: Program continues.
False: Program stops and prints file/line number.

Structs and Pointers

struct student {
    char name[50];
    unsigned int id;
    unsigned int age;
};

Variable Scopes

Global: Visible to the whole file.
Local: Visible inside block or function.
Static: Local but persistent.
Extern: Visible through multiple files.

Call by Value vs Reference

Call by Value: Argument is copied to the parameter.
Call by Reference: Pointer is passed to modify the original variable.

Related entries:

Tags:

data types C programming call by reference C language C strings ASCII malloc programming syntax call by value operators control structures structs arrays memory management pointers dynamic allocation