1 cse 324 - computer programming “using c-language” lectures 1

1

CSE 324 - Computer Programming“Using C-Language”

Lectures 1

Mohamed Shalan CSE 324 - Computer

Programming 2

Logistics

Grading Policy Final : 75% Mid-Term : 10% Homework : 5% Project : 10%

General Rules Attend 75% of tutorial sessions Late submission -> No Credit!


Programming 3

Logistics

Email: [email protected] Don’t send anything unrelated to the class Don’t insert me into your address book Make the subject line “CSE 324” Don’t use any language other than English

language Make sure that your name is included in the email


Programming 4

Logistics


Programming 5

Question

Why do we write programs?


Programming 6

Hardware vs. Software

A computer is made up of hardware and software

Hardware Software• CPU

-e.g. Intel Core 2 Duo• Input/Output devices

- keyboard- monitor- mouse

• main memory- e.g. 2GB RAM

• secondary memory- e.g. 120 GB hard drive

• operating systems- Windows XP- Mac OS X- Unix / Linux

• applications- games- Microsoft Word- Internet Explorer


Programming 7

Programs

A program is a set of instructions for a computer to follow

Following the instructions is called running or executing the program.


Programming 8

Running a Program

Sometimes the computer and the program are considered to be one unit. Programmers typically find this view to be more

convenient.


Programming 9

Low-level language(Machine language

/assembly language)

Programming Languages

High-level Programming

Languages (e.g. Java)human readable

computer readable

Compiler

translated by


Programming 10

Low-level language(Machine language

/assembly language)

Programming Languages

High-level Programming

Languages (e.g. Java)human readable

computer readable

Compiler

translated by

Source code

Object code


Programming 11

sterilize(saw,alcohol);raise_hammer();lower hammer(fast);start(saw);/* etc. etc. */

Patient has elevated pressure in anterior parietal lobe

The Problem-solving Process

"Doctor, my head hurts"

Problem

specification

Algorithm

Program

Executable (solution)

Design

Implementation

Compilation

Analysis


Programming 12

The Problem-solving Process

Problem specification

Algorithm

Program

Executable (solution)

Analysis

Design

Implementation

Compilation


Programming 13

A sequence of instructions specifying the steps required to accomplish some task

Named after:Muhammad ibn Musa al-Khwarizmi of Khowarezm (now Khiva in Uzbekistan)

Algorithm


Programming 14

Algorithm –History

Muhammad ibn Musa Al-Khwarizmihttp://www-groups.dcs.st-andrews.ac.uk/~history/Mathematicians/Al-Khwarizmi.html

Book on arithmetic: Hindu numeration, decimal numbers, use of zero,

method for finding square root Latin translation (c.1120 CE): “Algoritmi de numero

Indorum” Book on algebra

Hisab al-jabr w’al-muqabala


Programming 15

A sequence of instructions describing how to do a task

Algorithm – Working Definition


Programming 16

Algorithm -- Examples

A cooking recipe Assembly instructions for a model The rules of how to play a game VCR instructions A car repair manual


Programming 17

From Algorithms to Programs

Problem

C ProgramC Program

AlgorithmAlgorithm: A sequence of instructions describing how to do a task (or process)


Programming 18

Components of an Aalgorithm Variables and values Instructions

Sequences Procedures Selections Repetitions

Also required: Documentation


Programming 19

Values

Represent quantities, amounts or measurements

May be numerical or alphabetical (or other things)

Often have a unit related to their purpose Example:

Recipe ingredients


Programming 20

Variables

This jarcan contain

10 cookies

50 grams of sugar

3 slices of cake

etc.

Values

Variable

• Are containers for values – places to store values

• Example:


Programming 21

Restrictions on Variables

Variables may be restricted to contain a specific type of value


Programming 22

Components of an Algorithm

Values and Variables Instruction (a.k.a. primitive)

Sequence (of instructions) Procedure (involving instructions) Selection (between instructions) Repetition (of instructions)

Documentation (beside instructions)


Programming 23

Instructions (Primitives)

Some action that is simple unambiguous that the system knows about... ...and should be able to actually do


Programming 24

Instructions -- Application

Some instructions can only be applied to a specific type of values or variables

Examples:


Programming 25

Sequence

A series of instructions ...to be carried out one after the other... ...without hesitation or question Example:

How to cook a Gourmet MealTM


Programming 26

Sequence -- Example

1. Open freezer door 2. Take out Gourmet Meal™ 3. Close freezer door 4. Open microwave door 5. Put Gourmet Meal™ on carousel 6. Shut microwave door 7. Set microwave on high for 5 minutes 8. Start microwave 9. Wait 5 minutes 10. Open microwave door 11. Remove Gourmet Meal™ 12. Close microwave door


Programming 27

Procedure

A named sequence of instructions So that you can

Refer to it collectively (by name) ...instead of individually (by each instruction in the

sequence) Example:

Drive_To_Uni


Programming 28

Procedure -- Example procedure Drive_To_Uni { 1. find car keys 2. disable car alarm 3. open car door 4. get in car 5. shut car door 6. put keys in ignition 7. start car 8. back car out of

driveway 9. drive to end of street 10. turn right 11. drive to end of street 12. turn left ...etc...etc...etc

...etc...etc...etc...

52. find parking space

53. pull into parking space

54. turn off engine

55. remove keys from ignition

56. open car door

57. get out

58. shut car door

59. lock car door

60. enable alarm

}


Programming 29

Procedure – Example (cont)

procedure Do_Wednesday{ Wake_up Have_Shower Eat_Breakfast Drive_To_Uni Sit_1301_Lecture ...etc...etc...etc... Drive_From_Uni ...etc...etc...etc...}

procedure Do_Week

{

Do_Monday

Do_Tuesday

Do_Wednesday

Do_Thursday

...etc...etc...etc...

}


Programming 30

Selection

An instruction that decides which of two possible sequences is executed

The decision is based on a single true/false condition

Examples: Car repair


Programming 31

Selection Example -- Car Repair

if (motor turns) then {

CheckFuelCheckSparkPlugsCheckCarburettor

}else {

CheckDistributorCheckIgnitionCoil

}


Programming 32

Selection Example – Car Repair (cont)if (motor turns) then {


}else {


}

Should be a true or false condition.


Programming 33

Selection Example – Car Repair (cont)if (motor turns) then {


}else {


}

Sequence if the condition is true.


Programming 34

Selection Example – Car Repair (cont)

if (motor turns) then {


}else {


}

Sequence if the condition is false.


Programming 35

Repetition

Repeat an instruction... ...while (or maybe until) some true or false

condition occurs Test the condition each time before

repeating the instruction Also known as iteration or loop Example:

Algorithm used by a kid to convince his mom to buy a toy


Programming 36

Repetition -- Example

procedure Ask ( toy )

{

Say("Hey mom; I want to buy a“, toy)

ListenToReply ( )start begging count at zerowhile (reply is "No" and begging count < 100){ Say("Oh please!")

add 1 to begging count

ListenToReply ( )}

}


Programming 37

Repetition – Example (cont)

procedure Ask ( toy ){

Say("Hey mom; I want to buy a“, toy)ListenToReply ( )start begging count at zerowhile (reply is "No" and begging count < 100){ Say("Oh please!") add 1 to begging count ListenToReply ( )}

}

Condition is tested before sequence


Programming 38




}

Sequence may not get executed at all


Programming 39




}

Ensure initial values of variables used in the conditions are set correctly


Programming 40




}

Ensure the variables used in the conditions are updated in each iteration


Programming 41




} Infinite loop

• What if we don’t increment the begging count?


Programming 42

Documentation

Records what the algorithm does Describes how it does it Explains the purpose of each component of

the algorithm Notes restrictions or expectations


Programming 43

From Algorithms to Programs

Both are sets of instructions on how to do a task Algorithm:

talking to humans, easy to understand in plain (English) language

Program: talking to computer (compiler) can be regarded as a “formal expression” of an algorithm


Programming 44

High-Level Language

Compilers and linkers translate a high level program into executable machine code.

#include <stdio.h>

int main(){ printf(“Hello World”);

return 0;}

Source code Executable code

10100110 0111011000100110 0000000011111010 1111101001001110 1010011011100110 1001011011001110 0010111010100110 0100111011111010 0110011001001110 10000110

etc...


Programming 45

Developing a C Program

Use Text Editor to edit the “source file” (.c).

Editor + Compiler + Linker + Debugger = IDE

Debugging: Finding logical error (bugs) and eliminate them.

1 cse 324 - computer programming “using c-language” lectures 1

Documents