Syntax, Variables, Data Types, Constants, and Input Output

Basic Syntax Rules

C is case-sensitive. Statements usually end with semicolons. Blocks are defined using braces. Variables must be declared before use. Unlike some higher-level languages, C expects the programmer to be precise about types and storage.

Primitive Data Types

Type size can depend on platform and compiler, so students should focus first on meaning and usage, then later on exact memory-level implications.

Declaring Variables and Constants

int age = 21;
double price = 49.99;
char grade = 'A';
const int DAYS_IN_WEEK = 7;

const expresses intent clearly and helps prevent accidental modification.

Formatted Output and Input

#include <stdio.h>

int main(void) {
    int age;
    printf("Enter your age: ");
    scanf("%d", &age);
    printf("You entered: %d\n", age);
    return 0;
}

printf and scanf are fundamental, but beginners must be careful with format specifiers and addresses. The & operator in scanf is one of the first hints that C deals directly with memory addresses.

Format Specifiers

• %d for int
• %f for float and double in printf
• %c for char
• %s for strings
• %ld for long

Real-World Usage Snapshot

Even experienced engineers working with advanced systems still rely on clear understanding of primitive types, input-output formatting, and type discipline. Bugs in these basics can lead to wrong calculations, crashes, or undefined behavior later.