Lecture 1

Introduction To Computers

by

Jumail Bin Taliba

Faculty of Computer Science & Information System

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 1

Today’s Topics

•Computer Systems •Computing Environments •Computer Languages •System Development

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 2

Figure 1-1: A computer system Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 3

Figure 1-2: Basic hardware components Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 4

Computer Hardwares

– Five main components

• Input devices – Allows communication to the computer • Output devices – Allows communication to the user • Processor (CPU) • Main memory (primary storage) – Memory locations containing the running program • Secondary memory (auxiliary storage) – Permanent record of data often on a disk

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 5

Computer Memory

• Main Memory

– Long list of memory locations • Each contains zeros and ones • Can change during program execution – Binary Digit or Bit • A digit that can only be zero or one – Byte • Each memory location has eight bits – Address • Number that identifies a memory location

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 6

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 7

Larger Data Items

• Some data is too large for a single byte

– Most integers and real numbers are too large – Address refers to the first byte – Next few consecutive bytes can store the additional bits for larger data

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 8

Data or Code?

• ‘A’ may look like 01000001 • 65 may look like 01000001 • An instruction may look like 01000001 • How does the computer know the meaning of 01000001?

– Interpretation depends on the current instruction

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 9

Secondary Memory

• Main memory stores instructions and data while a program is running.

• Secondary memory

– Stores instructions and data permanently – A file stores data or instructions in secondary memory

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 10

Secondary Memory Media

• A computer might have any of these types of secondary memory – Hard disk • Fast • Fixed in the computer and not normally removed – Floppy disk • Slow • Easily shared with other computers – Compact disk • Slower than hard disks • Easily shared with other computers • Can be read only or re-writable

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 11

The Processor

• Typically called the CPU

– Central Processing Unit – Follows program instructions – Typical capabilities of CPU include: add subtract multiply divide move data from location to location

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 12

Figure 1-3: Types of software Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

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Figure 1-4: Software Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

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Figure 1-5: Personal computing environment Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

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Figure 1-6: Time-sharing Environment Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

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Figure 1-7: Client-server environment Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

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Figure 1-8: Types of computer languages Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 18

Example:

Machine Language:

the only language understood by a computer

0101 1000 0001 0000 0101 1011 0001 0000 0101 0000 0001 0000

Assembly/Symbolic language

MOVE #$1,D1 MOVE #$8,D0 ADD D0,D1

High-level language

LUAS = PANJANG * LEBAR IF LUAS > 50 GOTO BESAR ELSE GOTO KECIL

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 19

Figure 1-9: Building a C program Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

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Figure 1-10: Executing programs Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 21

Figure 1-11: Process of system development Building programs

•Edit •Compile •Link •Run

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 22

Figure 1-11: Process of system development Understand the problem:

•Input •Output •Process

Develop the solution

( Algorithm

•Structure chart •Pseudocode •Flowchart

):

Converting design to computer codes.

e.g: Flowchart -> C program Algorithm is the steps to solve problems

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 23

Testing and Debugging

• Bug – A mistake in a program • Debugging – Eliminating mistakes in programs – Term used when a moth caused a failed relay on the Harvard Mark 1 computer. Grace Hopper and other programmers taped the moth in logbook stating: “First actual case of a bug being found.”

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 24

Program Errors

• Syntax error – Violation of the grammar rules of the language – Discovered by the compiler • Error messages may not always show correct location of errors • Run-time error – Error detected by the computer at run-time • Logic error – Error in the program’s algorithm – Most difficult to diagnose – Computer does not recognize it.

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 25

Program Errors

(cont.)

Syntax error example

x = 2; y = 3 z = x + y;

This line consists an error. Each statement must be ended with a semi-colon ‘;’

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 26

Program Errors

(cont.)

Run-time error example

x = 0; y = 3/x;

This line produces an error, because the division by zero. This error is only discovered when the program runs.

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 27

Program Errors

(cont.)

Logic error example

Enter a number >>

10

Enter another number

>> 25

The

total

of those two numbers is

15

This is a logic error. The total should be 35 not 15.

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 28

Program Design • Structure Chart • Pseudo-code • Flowchart

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 29

Structure Chart

Represents a program as a collection of sub-programs (modules) Example:

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 30

Pseudo code

Describe an algorithm in English-like statements Example: Algorithm for multiplying two numbers 1. Get the first number, let say A 2. Get the second number, let say B 3. Calculate the result let say C, C= A * B 4. Display the result, C

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 31

Flowchart

Represents an algorithm in graphical symbols

Example: Algorithm for multiplying two numbers Start Get A Get B Calculate Resut C=A*B Display the Result C Stop

Chapter 1: Introduction To Computer

| SCP1103 Programming Technique C | Jumail, FSKSM, UTM, 2005 | Last Updated: July 2005

Slide 32