1. Introduction to Computer Programming
Featuring: C language

2. What is computer?
Computer is a device which can process data, perform computation and logical operations and gives output
A computer performs the above using programs and without human intervention

3. History and Hardware Babbage’s analytical engine (1822)
Atanasoff-Berry Computer (ABC, 1937)
Human operator manipulated external wiring
Electrical Numerical Integrator and Computer (ENIAC, 1946)
Vacuum tubes
Mark I (1944)
Mechanical relay switches
Electronic Delayed Storage Automatic Computer (EDSAC, 1949)
Incorporated a form of memory

4. History and Hardware (continued)

5. Computer Hardware & Software
Hardware – the physical devices of a computer
Software – the programs or “intelligence” of the computer

6. Software Software – a group of programs
Program – a specific set of instructions to the computer to perform a task
Programmer – a person who writes a program

7. Computer Organization
Input Unit
Output Unit
Memory Unit
Arithmetic Logic Unit (ALU)
Central Processing Unit (CPU)
Secondary Storage unit

8. Components

9. Memory and data Memory unit: Area to store data and instructions
Data stored as On or Off pulses

10. Data representation
Represented by a combination of eight binary digits (1s and 0s)
ASCII – American Standard Code for Information Interchange

11. ASCII representation
From to ; each assigned to a unique character.
An integer
is stored in memory in its binary equivalence
read as character using its ASCII character

12. ASCII Table

13. PROGRAMMING LANGUAGES

14. Programming Languages
Computer program: data and instructions used to operate a computer and produce a specific result
Programming: writing instructions in a language that the computer can respond to and that other programmers can understand
Programming language: set of instructions that can be used to construct a program
Source programs/Source code: Programs written in a computer language

15. Three General Types of Programming Languages:
1940s – Machine Languages
A natural language of a computer, machine dependent
the only language that can be understood and processed directly by computer
1950s – Symbolic/Assembly languages
use of a series of mnemonics to represent commonly used instructions
1960s – High-Level Languages
E.g. COBOL, FORTRAN, C, Java
Note:
Machine and assembly languages are low-level languages because they both use instructions that are directly tied to one type of computer

16. Machine Language
Executable program: program that can operate a computer
Executable programs are written with binary numbers, which is a computer’s internal language (machine language)
An example of a simple machine language program containing two instructions is:
Opcode is short for operation code; tells the computer the operation to be performed

17. Assembly Language
Assembly language: uses the substitution of word-like symbols for the opcodes, and decimal numbers and labels for memory addresses
LOAD first
ADD second
MUL factor
STORE answer

18. Assembly Language (continued)

19. Earlier high-level programming languages
COBOL (Common Business Oriented Language)
used primarily for business processing
FORTRAN (Formula Translation)
primarily perform mathematical calculations

20. Later High-Level Programming Languages
PL/I, BASIC, Pascal, Prolog, C, Ada
C++, Visual Basic
HTML, Java

21. Writing, Editing, Compiling and Linking Programs
Step1 – Write and edit programs
Step2 – Compile programs
Translate source file into machine language
The output produced by the compiler is called an object program (machine language version of the source code)
Step3 – Linking Programs
- combines additional machine language code with the
object program to create a final executable program

22. Writing, Editing, Compiling and Linking Programs

23. Procedural and Object-Oriented Languages
Procedural language: instructions are used to create self-contained units, called procedures
Procedure: accepts data as input and transforms it in some manner to produce a specific result as output
Also called function or method
Procedures conforming to structure guidelines are known as structured procedures

24. Procedural and Object-Oriented Languages (continued)
Structured language: high-level procedural language (e.g., C) that enforces structured procedures
Object-oriented languages: languages with object orientation such as C++, Java, Visual Basic, and C#

25. Procedural and Object-Oriented Languages (continued)

26. Structured programming
A technique for organizing and coding computer programs in which a hierarchy of modules is used
A disciplined approach in writing programs so that it is easier to test, debug and modify.
Example:
Pascal, Ada, C

27. History of C language
Developed in the 1970s at AT&T Bell Laboratories by K. Thompson, D. Ritchie, and B. Kernighan
Evolved from a language called B in the seventies at AT&T Bell labs
First implemented on the UNIX operating system
Written to help non-scientists develop computer programs
High-level structured language
Can also access the internal hardware of a computer
C permits a programmer to “see into” a computer’s memory and directly alter data stored in it
Standard maintained by the American National Standards Institute (ANSI)
In the 1980s, Bjarne Stroustrup (working at AT&T) developed C++
C with object-oriented capabilities

28. The C language General purpose programming language
Modern control flow and data structure
Uses economy of expression
Convenient and effective
Useful for writing compilers and operating systems

29. Characteristic of C language
Features structured programming
Top-down: System overview -> Subsystem refined in detail
Advantages of top-down programming:
Separating the low level work from the higher level objects leads to a modular design.
Modular design means development can be self contained.
Having "skeleton" code illustrates clearly how low level modules integrate.
Code is easier to follow, since it is written methodically and with purpose.

30. The Making of A Quality Program
Readability
understandable, with comments and documentations, using conventions like name of variables and indentations
Modularity
problems divided into sub-problems and assembled in a logical order
Efficiency
runs faster and smaller size of program

31. The Making of A Quality Program (cont.)
Robustness
Be able to handle all situations in a graceful manner
Not to crash in unexpected situations or go to infinite loops
Usability
correct, meets the end-user requirement

32. Q & A