Source Code (.c): Written by programmer. E.g., `program.c`
Preprocessed Code (.i): After preprocessor directives (e.g., `#include`, `#define`) are handled. E.g., `program.i`
Assembly Code (.s): After compilation to assembly language. E.g., `program.s`
Object Code (.o / .obj): Machine code for the specific source file. Not yet executable. E.g., `program.o`
Executable File (.exe): After linking all object files and libraries. Can be run. E.g., `a.out` (Linux) or `program.exe` (Windows).

Algorithm: A step-by-step procedure to solve a given problem.
- Characteristics: Unambiguous, finite, effective, input, output.
Flowchart: A graphical representation of an algorithm using standard symbols.
- Symbols: Oval (Start/End), Rectangle (Process), Parallelogram (Input/Output), Diamond (Decision), Arrows (Flow lines).

if statement:

if (condition) {
  // code if condition is true
}

if-else statement:

if (condition) {
  // code if true
} else {
  // code if false
}

else-if ladder:

if (condition1) {
  // code if condition1 true
} else if (condition2) {
  // code if condition2 true
} else {
  // code if no condition true
}

switch statement:

switch (expression) {
  case value1:
    // code block
    break;
  case value2:
    // code block
    break;
  default:
    // default code
}

for loop: For known number of iterations.

for (initialization; condition; increment/decrement) {
  // code to be executed
}

while loop: For unknown number of iterations, condition checked at start.
```
while (condition) {
  // code to be executed
}
```
do-while loop: For unknown number of iterations, condition checked at end (executes at least once).
```
do {
  // code to be executed
} while (condition);
```
break: Terminates the loop.
continue: Skips current iteration, proceeds to next.

Collection of elements of the same data type stored at contiguous memory locations.
Declaration: dataType arrayName[size];
- Example: int numbers[5];
Initialization: int arr[3] = {10, 20, 30};
Accessing elements: arrayName[index] (index starts from 0).
- Example: numbers[0] = 100;
Multi-dimensional Arrays: int matrix[3][3];

An array of characters, terminated by a null character ('\0').
Declaration: char str[50]; or char str[] = "Hello";
Input/Output: scanf("%s", str);, printf("%s", str);
- gets(), puts() for strings with spaces.
String Functions (from <string.h>):
- strlen(str): Length of string.
- strcpy(dest, src): Cop