Unit I: Introduction to Programming
1. Computer Programs & Languages
A Computer Program is a precise set of instructions given to a computer to perform a specific task.
- Natural Language: Languages used by humans for communication (like English or Hindi), which are often ambiguous and flexible.
- Programming Language: A formal language with strict rules (syntax) used to communicate instructions to a computer.
2. Levels of Programming Languages
Programming languages are categorized based on their distance from the computer hardware.
- Machine Level Language: The lowest level, consisting of binary code (0s and 1s) that the CPU executes directly.
- Assembly Level Language: Uses mnemonic codes (like ADD, SUB) instead of binary, requiring an Assembler for translation.
- High-level Programming Language: Human-readable languages (like C, Python) that are independent of the computer's hardware architecture.
3. Compiler and Interpreter
High-level code must be translated into machine code for execution.
| Feature | Compiler | Interpreter |
|---|---|---|
| Translation | Translates the entire program at once. | Translates the program line-by-line. |
| Execution Speed | Faster, as translation is done before running. | Slower, as translation happens during execution. |
| Error Reporting | Lists all errors after scanning the whole file. | Stops execution at the first error found. |
4. Core Programming Terms
Essential terminology used in software development:
- Source Code: The original code written by the programmer in a high-level language.
- Target Code: The output produced by the compiler, usually machine code.
- Compiling: The process of converting source code into machine code.
- Warning: A message from the compiler about potential issues that don't stop the program from running but might cause bugs.
- Debugging: The process of finding and fixing errors in the code.
- Testing: Verifying the program's output against expected results to ensure correctness.
5. Errors in Computer Programs
Errors, or "bugs," prevent a program from working correctly.
Types of Errors:
- Syntax Errors: Violations of the language's grammar rules (e.g., a missing semicolon). The compiler will catch these.
- Logical Errors: The program runs but gives the wrong result because the underlying logic is flawed.
- Runtime Errors: Errors that occur while the program is running, such as dividing by zero or running out of memory.
Exam Tips
- Compiler vs. Interpreter: This is a high-frequency question. Focus on the "line-by-line" vs. "whole program" distinction.
- Source Code: Remember that source code is human-readable, whereas target code is computer-readable.
- Debugging vs. Testing: Debugging is fixing a known issue; testing is looking for issues.
Frequently Asked Questions
Q: Why do we need High-level languages if the computer only understands binary?
High-level languages are easier for humans to write, read, and maintain. Compilers take care of the translation into machine code.
Q: Does a warning stop my program from running?
No, a program can still run with warnings, unlike errors which prevent compilation. However, it is best practice to fix warnings to avoid unpredictable behavior.