C Language Chapter Overview

Study Notes

C Language Overview

C is a widely-used programming language that provides low-level access to memory and is suitable for system programming.
Programs in C are structured using functions, variables, and control structures, allowing for detailed manipulation of data.

Variables

A variable is a named memory location used to store data.
Rules for naming variables:
- Case-sensitive (e.g., Var and var are different).
- Must start with an alphabet or underscore (_).
- Cannot contain spaces or special characters, except underscores.
Example of variable declaration:
```
int number = 25;
```

Data Types

Defines the type of data a variable can hold, affecting memory usage and operations.
Common data types and their sizes:
- char: 1 byte
- int: 2 bytes
- float: 4 bytes
- double: 8 bytes
- long: 4 bytes
C does not have built-in boolean or string data types.

Constants

Constants are values that do not change during program execution.
- Types include:
  - Integer Constants: e.g., 1, -2
  - Real Constants: e.g., 2.0, -24.8
  - Character Constants: e.g., 'a', '#'

Keywords

Reserved words with special meaning in C, totaling 32, including:
- auto, break, char, if, else, for, void, while, return
Keywords cannot be used as identifiers for variables or functions.

Program Structure

Basic structure of a C program includes preprocessor directives, a main function, and return statement.
```
#include <stdio.h>
int main() {
    printf("Hello World");
    return 0;
}
```

Comments

Used to annotate code, improving readability.
- Single-line: // comment
- Multi-line: /* comment */

Input and Output

Outputs data with printf function, supports various format specifiers:
- Integers: %d
- Floats: %f
- Characters: %c
Inputs data with scanf function using the corresponding format specifiers.

Compilation Process

The C source file is converted into an executable by a compiler.
- e.g., Hello.c compiles to a.exe (Windows) or a.out (Linux/macOS).

Instructions and Operators

C instructions are statements executed by the computer, including type declarations and arithmetic operations.
Types of operators include:
- Arithmetic: +, -, *, /, %
- Relational: ==, !=, >, <, >=, <=
- Logical: &&, ||, !

Arithmetic Operations

Utilizes operators for performing calculations:
- Example: a + b adds values of a and b.
Modulo operator (%) returns the remainder of a division.
- Example: 5 % 3 results in 2.

Variable Assignment and Expressions

Variables can be assigned values using =.
Expressions can combine variables and constants to compute values.

Control Flow

C provides control instructions for program execution flow:
- Sequence Control
- Decision Control (e.g., if, else)
- Loop Control (e.g., for, while)

Type Conversion

Implicit Conversion is performed by the compiler when mixing different data types.
Explicit conversion requires manual intervention by the programmer.
Operations on different types follow specific rules, impacting the output type.

Operator Precedence and Associativity

Operator precedence determines the order in which operations are performed:
- Highest: *, /, %
- Lower: +, -
Associativity for operators is left to right, affecting evaluation order in expressions.

Program Example

Summation program to demonstrate C syntax:

#include <stdio.h>
int main() {
    int a, b;
    printf("Enter a: ");
    scanf("%d", &a);
    printf("Enter b: ");
    scanf("%d", &b);
    int sum = a + b;
    printf("Sum is: %d", sum);
    return 0;
}