C Basic Syntax

This chapter introduces the basic syntax rules of C: identifiers, keywords, data types, statements, expressions, comments, code style, etc.

1. Identifiers and Naming Conventions

• Composed of letters, numbers, underscores, cannot start with a number
• Case sensitive
• Recommended to use meaningful lowercase with underscores (snake_case)

2. Keywords

Examples: int, char, float, double, if, else, switch, for, while, do, return, break, continue, sizeof, typedef, struct, union, enum, const, static, volatile, etc.

3. Statements and Semicolons

Each statement ends with a semicolon ;, code blocks are wrapped with curly braces {}.

4. Variables and Constants

const int MAX = 100; // constant
int a = 10;          // variable

5. Expressions and Operators

int x = 3 + 4 * 2; // operator precedence: multiplication before addition
x += 5;            // compound assignment
int y = (x > 10) ? 1 : 0; // conditional operator

6. Input and Output

#include <stdio.h>
int a; scanf("%d", &a);
printf("a=%d\n", a);

Common format specifiers: %d, %u, %ld, %f, %lf, %c, %s, %p.

7. Control Structures

• Conditional: if/else, switch
• Loops: for, while, do-while
• Jumps: break, continue, return

8. Functions

int add(int a, int b) { return a + b; }
int main(void) { printf("%d\n", add(2,3)); return 0; }

9. Header Files and Preprocessing

#include <stdio.h>