Chapter 8: Getting Started with C

Definition: A set of words and symbols used to write programs. Means of communication between user and computer.

Types:

• Low Level Language: Close to hardware, far from human language.
  • Machine Language: Native language (0s and 1s). Fast execution, no translator needed, machine dependent, difficult to learn.
  • Assembly Language: Uses mnemonics (English-like words) instead of binary. Needs Assembler. One step higher than machine language.
• High Level Language: Close to human language (English-like). Machine independent, easy to learn/debug. Needs Compiler/Interpreter. Examples: C, C++, Java, BASIC.

Software that converts high-level language programs into machine language.

• Compiler: Converts whole program into object code at once. Generates error map. Fast execution. (e.g., C Compiler).
• Interpreter: Converts program line-by-line. Stops at first error. Slower execution. No object code reused. (e.g., BASIC).
• Assembler: Converts Assembly language code into Machine language.

History: Developed by Dennis Ritchie at AT&T Bell Labs in 1972. Derived from B language (Ken Thompson). ANSI C standard developed later.

Characteristics:

• Convenient: Easier than low-level languages.
• Structured: Modular approach (functions).
• Machine Independent: Code runs on different processors (Intel, Motorola).
• Case Sensitive: Distinguishes uppercase/lowercase (e.g., 'A' != 'a').
• Hardware Control: Can write system software (Drivers, OS).
• Small Language: Few keywords but powerful.

IDE (Integrated Development Environment): A software suite to create, edit, compile, and debug programs (e.g., Turbo C++).

Steps to Prepare C Program:

1. Create/Edit: Use Text Editor. Save with .c extension.
2. Save: F2 (Default: NONAME00.CPP). Saved in BIN directory.
3. Compile: Alt + F9. Converts source code (.c) to object code (.obj). Checks syntax errors.
4. Link: Links object code with library files (.lib). Creates executable file (.exe).
5. Load: Loader places .exe into memory.
6. Execute: Ctrl + F9. Runs program. Output screen (Alt + F5).

Consists of 3 main parts:

1. Preprocessor Directives: Instructions to compiler before execution. Start with #.
   • #include <header.h>: Includes library files.
   • #define: Defines constants/macros.
2. Main Function: void main(void) { ... }. Execution starts here. Essential for every C program.
3. Program Body (C Statements): Enclosed in braces { }. Statements end with semicolon ;. Case sensitive.

• Syntax Error: Violation of language rules (e.g., missing semicolon). Detected by compiler.
• Logical Error: Poor logic (e.g., wrong formula). Program runs but gives wrong output. Most difficult to find.
• Runtime Error: Illegal operation during execution (e.g., divide by zero). Program crashes.