INTEC CS160 - Jeanine Ingber Engineering Problem Solving with C Fundamental Concepts Chapter 3 Control Structures and Data Files.

INTEC CS160 - Jeanine Ingber

Engineering Problem Solving with C

Fundamental Concepts

Chapter 3

Control Structures and Data Files


Algorithm Development


Structured Programming

Sequence

Selection

Repetition

yesno

yes

no


Conditional Expressions


Relational Operators

== equality != non equality < less than > greater than <= less than equal to >= greater than equal to


Logical Operators

! not && and || or


Operator Precedence

1 < <= > >=2 == !=3 &&4 ||


Selection Statements


Selection Statements

if if else switch


If statement

if(Boolean expression)

statement; //single statement if(Boolean expression)

{ //more than one statement

statement1;

.

statement n;

}


If statement - examples

• if (x>0)k++;

• if(x>0) {

x=sqrt(x);k++;

}


if - else statement

if(Boolean expression)statement;

elsestatement;

if(Boolean expression){

statement block}else{

statement block}


nested if-else

if(x > y)if(y < z)

k++;else

m++;else

j++;


Practice!

int x=9, y=7, z=2, k=0, m=0, j=0;if(x > y)

if(y < z)k++;

elsem++;

elsej++;

What are the values of j, k and m?


Switch Statement

switch(expression){

case constant:statement(s);break;

case constant:statement(s);break;

/* default is optional*/default:

statement(s);}


Switch Statement

Expression must be of type integer or character

The keyword case must be followed by a constant

break statement is required unless you want all subsequent statements to be executed.


Practice!

Convert the following nested if/else statements to a switch statement:

if (rank==1 || rank==2) printf("Lower division \n");else{ if (rank==3 || rank==4) printf("Upper division \n"); else { if (rank==5) printf("Graduate student \n"); else printf("Invalid rank \n"); }}


Loop Structures


repetition

while statement do while statement for statement


while statement

while(expression)statement;

while(expression){

statement;statement;

.}


do while

dostatement;

while(expression);

do{

statement1;statement2;

.} while(expression);

note - the expression is tested after the statement(s) are executed, so statements are executed at least once.


for statement

for(initialization; test; increment/decrement)

statement;

for(initialization; test; increment/decrement)

{

statement;

statement;

.

}


for statement

initalizetest

increment/decrement

true

statement(s)statement(s)


for statement - examples

int sum =0;for(int I=1;I<10;I+=2)

sum = sum + I;

int fact =1;for(int n=5;n>1;n- -)

fact = fact * n;


Practice!

Determine the number of times that each of the following for loops are executed.

for (k=3; k<=20; k++){statements;}for (k=3; k<=20; ++k){statements;}for (count=-2; count<=14; count++){statements;}


break statement

break;– terminates loop– execution continues with the first statement

following the loop


continue statement

continue;– forces next iteration of the loop, skipping any

remaining statements in the loop


Data Files


Data Files

Each data file must have a file pointer– file pointer must be defined

• FILE *sensor1;• FILE *balloon;

– file pointer must be associated with a specific file using the fopen function

• sensor1 = fopen(“sensor1.dat”, “r”);

• balloon = fopen(“balloon.dat”, “w”);


I/O Statements

Input file - use fscanf instead of scanf– fscanf(sensor1, “%1f %lf”, &t, &motion);

Output file - use fprint instead of printf– fprintf(balloon, “%f %f %f\n”, time, height,

velocity);


Reading Data Files

counter controlled loop– for loop

sentinel controlled loop– while loop

end of file controlled loop– while loop

INTEC CS160 - Jeanine Ingber Engineering Problem Solving with C Fundamental Concepts Chapter 3 Control Structures and Data Files.

Documents

statement n

n slide

switch slide

statement block

statement statement1

j slide

constant break statement

statement examples int