unimap sem1-07/08ekt120: computer programming1 week2

UniMAP Sem1-07/08

EKT120: Computer Programming

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Week2

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Outline Sample programming question Sample C program Identifiers and reserve words Program comments Preprocessor directives Data types and type declarations Operators Formatted input and output Program debugging

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Sample Programming Question

• Write a program that calculate nett income .Your program should read income from user. Given tax rate is 10% and epf rate is 5% from income.

• Steps: Analyze the problem Use algorithm Convert to actual codes

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Sample C Program//Program name : program1.c//Programmer : Yasmin//This program reads income and calculate nett income //after epf and tax deduction#include <stdio.h>

int main(void){

float income, net_income;const float epf=0.1, tax=0.05;

printf(“Enter income : “);scanf(“%f”, &income);net_income=income-(epf*income) – (tax*income);printf(“\nNett income : %5.2f”, net_income);return 0;

}

The terms void indicates we receive nothing from OS and

return an integer to OSVariable

&constant

declaration

begin

end

Return 0(int) to OS

body

Comments

Preprocessor directives

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Identifiers & Reserve Words Identifiers

labels for program elements case sensitive can consists of capital letters[A..Z], small

letters[a..z], digit[0..9], and underscore character _ First character MUST be a letter or an underscore No blanks Reserve words cannot be identifiers

Reserve words already assigned to a pre-defined meaning eg: delete, int, main, include, double, for, if etc.

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Program comments

Starts with /* and terminate with */ OR

Character // start a line comment, if several lines, each line must begin with //

Comments cannot be nested /* /* */*/

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Preprocessor directives An instruction to pre-processor Standard library header (p154,Deitel) E.g. #include <stdio.h>

for std input/output #include <stdlib.h>

Conversion number-text vise-versa, memory allocation, random numbers

#include <string.h> string processing

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Data Types & Mem. Alloc.

Data Type

DescriptionSize (byte

s)

charA single character. Internally stored as a coded integer value (refer to ASCII table).

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intInteger quantity. Can be represented in signed or unsigned form (with the unsigned keyword).

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float Floating-point number. Set of real numbers. 4

doubleA more precise version of float. Has larger dynamic range and better representation of decimal points.

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boolBoolean representation of logic states. Can only be assigned true (1) or false (0).

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Type declarations

float income;float net_income;

int index =0, count =0; char ch=‘a’, ch2; const float epf = 0.1, tax = 0.05;

float income, net_income;

Declare and initialize

Named constant declared and

initialized

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Types of operators Types of operators are:

Arithmetic operators (+ , - , * , / , %)

Relational operators (> , < , == , >= , <=, !=)

Logical operators (&& , ||) Compound assignment operator

(+=, -=, *=, /=, %=) Binary operators: needs two operands Unary operators: single operand Bitwise operators: executes on bit level

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Arithmetic Operators

Used to execute mathematical equations

The result is usually assigned to a data storage (instance/variable) using assignment operator ( = )

E.g sum = marks1 + marks2;

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Arithmetic OperatorsC Operation Arithmetic

OperatorAlgebraic expression

C expression

Addition + f + 7 f + 7

Subtraction - p – c p - c

Multipication * bm b * m

Division / x / y x / y

Remainder(Modulus)

% r mod s r % s

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Exercise on arithmetic operators

Given x = 20, y = 3 z = x % y = 20 % 3

= 2 (remainder)

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Relational and Logical Operators

Previously, relational operator: >, < >=, <=, == , != Previously, logical operator:

&&, || Used to control the flow of a program Usually used as conditions in loops

and branches

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More on relational operators Relational operators use mathematical

comparison (operation) on two data, but gives logical outpute.g1 let say b = 8, if (b > 10)e.g2 while (b != 10)e.g3 if(kod == 1) print(“Pegawai”);

Reminder:Don’t confuse == (relational op.) with = (assignment op.)

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More on logical operators

Logical operators are manipulation of logice.g1 let say b=8, c=10,

if ((b > 10) && (c<10))e.g2 while ((b==8) ||(c > 10))e.g3 if ((kod == 1) && (salary > 2213))

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Truth table for &&(logical AND) operator

exp1 exp2 exp1 && exp2

false false false

false true false

true false false

true true true

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Truth table for ||(logical OR) operator

exp1 exp2 exp1 || exp2

false false false

false true true

true false true

true true true

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Compund assignment operator To calculate value from expression and

store it in variable, we use assignment operator (=)

Compound assignment operator combine binary operator with assignment operator

E.g. val +=one; is equivalent to val = val + one; E.g. count = count -1; is equivalent to

count -=1;count--;--count;

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Unary Operators Obviously operating on ONE

operand Commonly used unary operators

Increment/decrement { ++ , -- } Arithmetic Negation { - } Logical Negation { ! }

Usually using prefix notation Increment/decrement can be both a

prefix and postfix

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Unary Operators (Eg.) Increment/decrement { ++ , -- }

prefix:value incr/decr before used in expression

postfix:value incr/decr after used in expression

Logical Negation { ! } bool isDinnerTime = true; bool isLunchTime = !isDinnerTime;

val=5;

printf(“%d”, ++val);

Output:

6

val=5;

printf(“%d”, --val);

Output:

4val=5;

printf(“%d”, val++);

Output:

5

val=5;

printf(“%d”, val--);

Output:

5

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Operator PrecedenceOperators Precedence

! + - first

* / % second

+ - third

< <= >= > fourth

== != fifth

&& sixth

|| seventh

= last

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Formatted Output with printf

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Formatted Output with printf-cont

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Formatted input with scanf

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Formatted input with scanf-cont

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Program debugging Syntax error

Mistakes caused by violating “grammar” of C C compiler can easily diagnose during

compilation Run-time error

Called semantic error or smart error Violation of rules during program execution C compiler cannot recognize during compilation

Logic error Most difficult error to recognize and correct Program compiled and executed successfully

but answer wrong

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Program debugging-syntax error snapshot

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Program debugging-run time error snapshot

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Program debugging-logic error snapshot

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End Week 1 – Session 2

Q & A!

unimap sem1-07/08ekt120: computer programming1 week2

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