ECSE 221 - Introduction to Computer Engineering - Tutorial 1 - Muhammad Ehtasham Ulhaque

Introduction to Computer Engineering ECSE 221 Muhammad Ehtasham Ulhaque [email protected] Tutorial 1 Winter 2011

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Why use C?

• Imperative programming language

• Provides language constructs that map efficiently to machine instructions

• Require minimal run-time support

• Provides low-level access to memory

Difference between C & Java

type of language function oriented object oriented

basic programming unit function class = ADT

portability of source code possible with discipline yes

portability of compiled code no, recompile for each architecture

yes, bytecode is "write once, run anywhere"

hello, world

#include<stdio.h> int main(void) { printf("Hello\n"); return 0; }

public class HelloWorld { public static void main(String[] args) { System.out.println("Hello"); } }

Source: http://www.cs.princeton.edu/introcs/faq/c2java.html

More to come as we go along

Pelles C –C Compiler

• WebCT

• Download and Install Pellas C

• Set up environment

• Build a simple program – Hello World!

C – General Structure

• Libraries

• Declarations

• Method Definition

• Main Method

Data Types

• Int: Integer

• Char: One byte character

• Float: Single-precision floating point

• Double: Double-precision floating point

Array Declaration:

• Array: int array[number][number]

Example 1

//libraries #include <stdio.h> #include <stdlib.h> #include <string.h> //declaration #define PI 3.14

float getRadius(){ float radius; printf(“Please enter the radius of the circle:\n”); scanf(“%f”,&radius); return(radius); }

Example 2 (contd.)

float getArea(float radius){

float area;

area = PI*radius*radius;

return area;

}

void main()

{

float circleradius= getRadius();

float localarea= getArea(circleradius);

printf("the area of a circle of radius %f is: %f",circleradius,localarea);

}

Basic I/O commands

• scanf: reads till a whitespace character (blank space,EOL,etc)

• Printf: outputs a line of text which can include variables

• Float and decimal types are items in a memory location thus

Scanf(“%f”,&numberlocation) The & specifies to store the content at memory location ‘numberlocation’

Characters

• \n :new line character

• <,>,==,!= : conditional operators

• +,-,/,* : arithmetic operators

• foo++ : use foo then increment

• ++foo: increment foo then use it

• +=,*=,/=,-=, syntax shortcut

If statements

If(<condition 1>)

<statement block 1>

else if(<condition 2>)

<statement block 2>

else

<statement block 3>

EXAMPLE:

If( x==‘+’)

printf(“the sum is %d”,a+b);

else if( x==‘/’)

printf(“the quotient is %d”,a/b);

While loop

While (<condition [booleanexpression]>)

<statement>

EXAMPLE

Int n=3;

Int number=5;

Int sum=0;

While (n>0){

sum = sum + number;

n--;

}

return sum;

For loop

For(<statement 1>;<condition> [booleanexpression];<statement 2>)

{

<statement block 3>

}

EXAMPLE

sum = 0;

number = 5;

for(int n=3; n>0;n--){

sum += number;

}

return sum;

Boolean operators

• &&: (AND)

a && b : a and b must both be equal to 1 -> ‘true’

• ||: (OR)

a || b : a and/or b must both be equal to 1

• ! : (NOT)

!a return the complement of a

Bitwise operators *

• & bitwise AND

• | bitwise OR

• ^ bitwise XOR

• << left shift

• >> right shift

• A & 0x0001 -> this return the last bit

Pointers

• Data type which points to another location in memory

4

a b

Location 1000 Location 1004 If we had a 32 bit machine

Address in byte

• int *a, b; • a is a pointer to an integer • b = 4;

a = &b;

1004 4

a b

Location 1000 Location 1004

is the content of the location ‘a’ (content at 1004) = 4 *a

Pointers (contd.)

• a is the address which the pointer contains: 0x0002

• *a is the content of the location ‘a’ (content at location 0x0002) : 4

• &a is the address of the pointer a: 0x0001

• b is the content at pointer b: 4

• &b is the address of pointer b: 0x0002

• *b illegal operation

Command line arguments

• void main(int argc, char *argv[])

• argc

• –Integers which is equal to the number of terms in the call

• argv

• –Array of pointers