1. Unit# 8: Introduction to Computer Programming

2. Learning Objectives In this unit you will be learn about:
Computer program
Types of languages (low & high level)
Editor, Translator (compiler & interpreter)
IDE
Source program, object program
Principles of structured and modular programming

3. Computer program
A computer program is a collection of instructions that performs a specific task when executed by a computer. A computer requires programs to function and typically executes the program's instructions in a central processing unit.
Series of instructions to a computer to accomplish a task
Instructions must be written in a way the computer can understand

4. Types of languages Programming Language:
A programming language is a special language programmers use to develop software programs, scripts, or other sets of instructions for computers to execute.
Three types of programming languages:
Machine language
Assembly language
High-level language

5. Machine Language
Only language of a computer understood by it without using a translation program
Normally written as strings of binary 1s and 0s
Written using decimal digits if the circuitry of the computer being used permits this

6. Machine Language
A Typical Machine Language Instruction Format

7. Machine Language
A Sample Machine Language Program

8. Machine Language Advantages & Limitations of Machine Language:
Can be executed very fast
Limitations
Machine Dependent
Difficult to program
Error prone
Difficult to modify

9. Assembly/Symbolic Language
Programming language that overcomes the limitations of machine language programming by:
Using alphanumeric mnemonic codes instead of numeric codes for the instructions in the instruction set e.g. using ADD instead of 1110 (binary) or 14 (decimal) for instruction to add
Allowing storage locations to be represented in form of alphanumeric addresses instead of numeric addresses e.g. representing memory locations 1000, 1001, and 1002 as FRST, SCND, and ANSR respectively
Providing pseudo-instructions that are used for instructing the system how we want the program to be assembled inside the computer’s memory e.g. START PROGRAM AT 0000; SET ASIDE AN ADRESS FOR FRST

10. An Example of Assembly Language Program

11. Advantages of Assembly Language Over Machine Language
Easier to understand and use
Easier to locate and correct errors
Easier to modify
No worry about addresses
Easily reloadable
Efficiency of machine language

12. Limitations of Assembly Language
Machine dependent
Knowledge of hardware required
Machine level coding
Typical Uses of Assembly Language:
Mainly used today to fine-tune important parts of programs written in a high-level language to improve the program’s execution efficiency

13. High--Level Languages
Machine independent
Do not require programmers to know anything about the internal structure of computer on which high-level language programs will be executed
Deal with high-level coding, enabling the programmers to write instructions using English words and familiar mathematical symbols and expressions

14. Advantages of High--Level Languages
Machine independent
Easier to learn and use
Fewer errors during program development
Lower program preparation cost
Better documentation
Easier to maintain

15. Editor
A source code editor is a text editor program designed specifically for editing source code of computer programs by programmers. It may be a standalone application or it may be built into an integrated development environment (IDE) or web browser.

16. Editor Concepts Editing a file is to modify the content of a file
Text editor:
Enter and modify text in a text file
Word processor:
Enter, modify and format text in a document
Line editor:
Edit file one line at a time
Unix examples: ex, ed and sed
Full screen editor
Shows a whole screen of text at a time

17. Editor features enter text search and replace copy, cut and paste
undo and redo
importing and exporting text
save and cancel
Types of editors:
EMACS Editor
PICO AND NANO EDITORS
GUI Editors

18. Translator
A translator is a computer program that performs the translation of a program written in a given programming language into a functionally equivalent program in a different computer language, without losing the functional or logical structure of the original code.
Types:
Assembler
Compiler
Interpreter

19. Assembler
Software that translates as assembly language program into an equivalent machine language program of a computer.

20. Compiler
Translator program (software) that translates a high-level language program into its equivalent machine language program
Compiles a set of machine language instructions for every program instruction in a high-level language

21. Interpreter Interpreter is a high-level language translator
Takes one statement of a high-level language program, translates it into machine language instructions
A program that can translate and execute a program line by line.
Immediately executes the resulting machine language instructions
Compiler simply translates the entire source program into an object program and is not involved in its execution

22. Program Errors Syntax Errors: Runtime error: Logical errors:
Errors in grammar of the language
Runtime error:
When there are no syntax errors, but the program can’t complete execution
Divide by zero
Invalid input data
Logical errors:
The program completes execution, but delivers incorrect results
Incorrect usage of parentheses

23. Integrated Development Environment (IDE)
An integrated development environment (IDE) is a software suite that consolidates the basic tools developers need to write and test software.
An integrated development environment (IDE) is a software application that provides comprehensive facilities to computer programmers for software development. An IDE normally consists of a source code editor, build automation tools and a debugger. 

24. Source Program
Source code is the fundamental component of a computer program that is created by a programmer.
A program written in a high-level language is called source code.
Source code is also called source program. Computer cannot understand the statements of high-level language.
The source code cannot be executed by computer directly. It is converted into object code and then executed.  

25. Object Program
A program in machine language is called objet code. It is also called object program or machine code. Computer understands object code directly.

26. Difference between source code and objet code
1. Source code is written in high-level or assembly language.
2. Source code is easy to understand.
3. Source code is easy to modify.
4. Source code contains fewer statements than object code.
Object code
1. Object code is written in machine language through compilers.
2. Object code is difficult to understand.
3. Object code is difficult to modify.
4. Object code contains more statements than source code.

27. Principles of structured and modular programming
Structured programming is the set of design and implementation processes that yield well-structured programs.
A disciplined approach to programming
Top-down design
Step-wise refinement using a restricted set* of program structures
* The set of program structures used in structured programming is:
Sequence
Choice
Loop

28. Top-Down Design
A program is divided into a main module and its related modules. Each module is in turn divided into sub modules until the resulting modules are understood without further division.

29. Modular Programming
Determine the major tasks that the program must accomplish. Each of these tasks will be a module.
Some modules will be complex themselves, and they will be broken into sub-modules, and those sub-modules may also be broken into even smaller modules.