🌟 C Language Primer

1 Primitive Types

C provides several built-in types. Common numeric types include:

int     a = 10;      // typically 4 bytes
long    b = 100000L; // typically 8 bytes
float   c = 3.14f;   // single-precision floating point
double  d = 3.14159; // double-precision floating point

Use sizeof() to check the exact size on your platform.

2 Function Definition

A function consists of a return type, name, parameters, and a body:

int add(int x, int y) {
    return x + y;
}

Usage:

int result = add(2, 3); // result = 5

3 Variables

Variables must be declared with a type:

int count = 42;
float ratio = 0.75;

Uninitialized variables contain garbage values.

4 Expressions

Expressions involve operators and operands:

int a = 5, b = 3;
int sum = a + b;
int product = a * b;
float quotient = (float)a / b;

C has standard arithmetic and logical operators.

5 Pointers and Arrays

5.1 Pointers

A pointer stores the address of another variable:

int x = 10;
int *p = &x;   // p points to x
*p = 20;       // x is now 20

5.2 Arrays

Arrays are contiguous blocks of elements:

int arr[3] = {1, 2, 3};
int first = arr[0];

Arrays and pointers are closely related:

int *ptr = arr;
printf("%d\n", ptr[1]); // prints 2

6 `if` Statements

Conditional execution:

int x = 10;
if (x > 0) {
    printf("Positive\n");
} else if (x == 0) {
    printf("Zero\n");
} else {
    printf("Negative\n");
}

7 `while` Statements

Loop while condition is true:

int i = 0;
while (i < 5) {
    printf("%d\n", i);
    i++;
}

8 `for` Statements

More compact loop syntax:

for (int i = 0; i < 5; i++) {
    printf("%d\n", i);
}

9 `typedef struct` Definitions

Custom types using struct and typedef:

typedef struct {
    int id;
    float grade;
} Student;

Student s = {123, 95.5};
printf("ID: %d, Grade: %.1f\n", s.id, s.grade);

You can also use the traditional style:

struct Student {
    int id;
    float grade;
};