Lecture 5 repetition statements

Ho Chi Minh City University of Technology
Faculty of Computer Science and Engineering

Chapter 5: Repetition Statements
Introduction to Computer Programming
(C language)
TS. Võ Thị Ngọc Châu
(,
)
2017 – 2018, Semester 2


Course Content
C.1. Introduction to Computers and
Programming
 C.2. C Program Structure and its
Components
 C.3. Variables and Basic Data Types
 C.4. Selection Statements
 C.5. Repetition Statements
 C.6. Functions
 C.7. Arrays
 C.8. Pointers
 C.9. File Processing


2


References


[1] “C: How to Program”, 7th Ed. – Paul
Deitel and Harvey Deitel, Prentice Hall, 2012.



[2] “The C Programming Language”, 2nd Ed.
– Brian W. Kernighan and Dennis M. Ritchie,
Prentice Hall, 1988



and others, especially those on the Internet

3


Content
 Introduction
 while..

Statements

 do..while..
 for..

Statements

Statements

 Nested

Repetition Statements

 continue
 break

Statements

Statements

 Summary
4


Introduction


Control statements in C


Sequence






Selection







Assignment
Function calling
…
if
if..else..
switch..case..

Repetition




for..
while..
do..while..
5


Introduction


Given a

void main() {

set of n

double positiveNumber[10] = {2, 1, 3, 10, 8, 3, 4, 5, 9, 12};

positive

double minNumber = positiveNumber[0];

numbers,

int iteration = 1;

int n = 10;

while (iteration < n) {

find the

if (minNumber <= positiveNumber[iteration])
iteration = iteration + 1;

smallest

else {

one.

minNumber = positiveNumber[iteration];
iteration = iteration + 1;

(Chapter 1 –

}
}

Real code in C)

Control Statements for Repetition

}
6


Introduction


A repetition statement allows you to specify
that an action is to be repeated while some
condition remains true.



Example 1: Input validation


Ask a user to input a value



While his/her input value is invalid, ask him/her
to input a value.



Example 2: Search for any of you who didn’t
submit homework (i.e. no attachment exists)



Example 3: Count the number of occurrences
of an important keyword in a text

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while.. Statements
while (<Condition>) <Statement>;
false (= 0)

while (<Condition>) {
<Statement1>;
…

<Statementk>;

<Condition>
true ( 0)
<Statements>

}


1. <Condition> is evaluated.



2. If <Condition> is true (0), <Statements> are performed
and then go to step 3. Otherwise, i.e. if <Condition> is false
(=0), go to step 4.



3. Go back to step 1.



4. End the repetition statement and move forward.

8


while.. Statements
false (= 0)

i<=3
true ( 0)

printf(…);
i++;

false (= 0)
i>=3
true ( 0)
printf(…);
i++;
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while.. Statements
Write a program to receive a natural number from a user. If an invalid
value is entered, ask the user to input again until a valid one is obtained.

10


while.. Statements
Given N, the number of the first natural numbers
greater than 0, calculate and print the total sum of
these N first natural numbers.

11


while.. Statements
Given N, a natural number greater than 0, calculate and print the
factorial of N: N! = 1*2*..*N = (N-1)!*N

12

Given a natural number N

greater than 0, list a series of
while.. Statements

Fibonacci numbers smaller than N.

13


do..while.. Statements
do {
<Statement1>;
…

<Statements>

<Statementk>;
}

true(0)
<Condition>

while (<Condition>);

false(=0)
<Statements> are always



1. <Statements> are performed.



2. <Condition> is evaluated.



3. If <Condition> is true (0), go to step 1. Otherwise, i.e. if
<Condition> is false (=0), go to step 4.



4. End the repetition statement and move forward.

performed at least once!

14


do..while.. Statements
printf(…);
i++;
true(0)

i<=3
false(=0)

printf(…);

i++;
true(0)
i>=3

false(=0)


do..while.. Statements
Write a program to receive a natural number from a user. If an invalid
value is entered, ask the user to input again until a valid one is obtained.

16


do..while.. Statements
Given N, the number of the first natural numbers
greater than 0, calculate and print the total sum of
these N first natural numbers.

17


do..while.. Statements
Given N, a natural number greater than 0, calculate and print the
factorial of N: N! = 1*2*..*N = (N-1)!*N

18


Given a sequence of N numbers input sequentially

by a user, find the minimum one.

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for.. Statements
<expression_1>
false (=0)
<expression_2>

true (0)
<Statements>

<expression_3>

for (<expression_1>; <expression_2>; <expression_3>) <Statement>;
for (<expression_1>; <expression_2>; <expression_3>) {
<Statement1>;
…
<Statementk>;
}

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for.. Statements
<expression_1>
false (=0)
<expression_2>

true (0)
<Statements>

<expression_3>

1.

<expression_1> is evaluated.

2.

<expression_2> is evaluated.

3.

If <expression_2> is true (0), <Statements> are performed,
<expression_3> is evaluated, and then go to step 2. Otherwise, i.e.
if <expression_2> is false (=0), go to step 4.

4.

End the repetition statement and move forward.

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for.. Statements
for (<expression_1>; <expression_2>; <expression_3>) <Statement>;

is regarded as:

<expression_1>;
while (<expression_2>) {
<Statement>;
<expression_3>;
}
for (<expression_1>; <expression_2>; <expression_3>) {
<Statement1>;
…
<Statementk>;
}
is regarded as:

<expression_1>;
while (<expression_2>) {
<Statement1>;
…
<Statementk>;
<expression_3>;
}

22


for.. Statements
i=1;
false (=0)
i<=3

true (0)
printf(…);

i++;

No printing result exists due to a false value of the expression “i>=3”.

23


for.. Statements
Given N, the number of the first natural numbers greater than 0,
calculate and print the total sum of these N first natural numbers.

24


for.. Statements
Given N, a natural number greater than 0, calculate and print the
factorial of N: N! = 1*2*..*N = (N-1)!*N

25