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Bài giảng Introduction to Computer Programming (C language) - Chapter 4: Selection statements - Võ Thị Ngọc Châu

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Ho Chi Minh City University of Technology  
Faculty of Computer Science and Engineering  
Chapter 4: Selection Statements  
Introduction to Computer Programming  
(C language)  
TS. Võ Thị Ngọc Châu  
([email protected]n,  
[email protected])  
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  
if.. statements  
if..else.. statements  
Nested if../if..else.. statements  
switch..case.. statements  
Summary  
4
Introduction  
Recall  
Statement  
ended with a semicolon (;)  
stretched on multiple lines with a backslash \ at the end  
able to be grouped in the brackets {}  
not consider spaces  
Block  
specified by {} with no semicolon after the right brace  
contains as many statements as required  
is a compound statement, syntactically equivalent to a  
single statement  
Sequentially processed from the beginning to the  
5
end of a function  
Introduction  
void main() {  
Given a  
double positiveNumber[10] = {2, 1, 3, 10, 8, 3, 4, 5, 9, 12};  
set of n  
positive  
numbers,  
find the  
smallest  
one.  
int n = 10;  
double minNumber = positiveNumber[0];  
int iteration = 1;  
while (iteration < n) {  
if (minNumber <= positiveNumber[iteration])  
Single  
statement  
iteration = iteration + 1;  
else {  
minNumber = positiveNumber[iteration];  
Block  
iteration = iteration + 1;  
(Chapter 1 –  
}
}
Real code in C)  
}
6
Introduction  
Control statements in C  
Sequence  
Assignment  
Function calling  
…  
Selection  
if  
if..else..  
switch..case..  
Repetition  
for..  
while..  
do..while..  
7
Introduction  
void main() {  
Given a  
double positiveNumber[10] = {2, 1, 3, 10, 8, 3, 4, 5, 9, 12};  
set of n  
positive  
numbers,  
find the  
smallest  
one.  
int n = 10;  
double minNumber = positiveNumber[0];  
int iteration = 1;  
while (iteration < n) {  
if (minNumber <= positiveNumber[iteration])  
iteration = iteration + 1;  
else {  
minNumber = positiveNumber[iteration];  
iteration = iteration + 1;  
(Chapter 1 –  
}
Control Statements for Selection  
}
Real code in C)  
}
8
if.. statements  
if (<Condition>) <Statement>  
false (0)  
<Condition>  
if (<Condition> )  
{
true (0)  
<Statements>  
}
<Statements>  
<Statements> is performed (selected)  
if <Condition> is true.  
Otherwise, ignored.  
if.. statements  
false (0)  
grade>=5.0  
true (0)  
printf(“Passed”);  
Print “Passed” if grade >= 5.0.  
Otherwise, ignored.  
10  
if..else.. statements  
if (<Condition>) <Statement T>  
else <Statement F>  
false (0)  
if (<Condition>) <Statement T>  
else  
{
<Condition>  
<Statements F>  
}
true (0)  
if (<Condition> )  
{
<Statements T>  
<Statements F>  
<Statements T>  
}
else <Statement F>  
if (<Condition> )  
{
<Statements T>  
}
else  
{
<Statements T> is performed (selected)  
if <Condition> is true.  
<Statements F>  
}
Otherwise, <Statements F> is performed.
if..else.. statements  
false (0)  
grade >= 5.0  
true (0)  
printf(“Passed”);  
printf(“Failed”);  
Print “Passed” if grade >= 5.0.  
Otherwise, print “Failed”.  
12  
if..else.. statements  
Conditional expression:  
<condition>?<expression T>:<expression F>  
can be regarded as:  
if (<condition>) <expression T>;  
else <expression F>;  
13  
if..else.. statements  
Which one do you prefer:  
conditional expressions or  
if..else.. statements?  
14  
Nested if../if..else.. statements  
if (<condition 1>)  
if (<condition 1>)  
{
{
…
…
if (<condition 2>) …  
if (<condition 2>) …  
…
…
}
}
else  
{
…
if (<condition 3>) …  
…
}
15  
Nested if../if..else.. statements  
16  
Nested if../if..else.. statements  
17  
Nested if../if..else.. statements  
A multi-way decision  
if (<condition 1>) <statements T1>  
else if (<condition 2>) <statements T2>  
else if (<condition 3>) <statements T3>  
…
else if (<condition k>) <statements Tk>  
else <statements Fk>  
18  
Nested if../if..else.. statements  
Be careful with specifying “else” for “which if”:  
if (<condition 1>)  
if (<condition 2>) <statements T2>  
else <statements F>  
should be:  
if (<condition 1>) {  
d = ? 5? 10? 20?  
if (<condition 2>) <statements T2>  
}
else <statements F1>  
or:  
if (<condition 1>) {  
if (<condition 2>) <statements T2>  
else <statements F2>  
d = ? 5? 10? 20?  
}
switch..case.. statements  
false (0)  
false (0)  
false (0)  
<case 1>  
<case 2>  
<case N>  
true (0)  
true (0)  
true (0)  
<Statements 1>  
<Statements 2>  
<Statements N>  
<Default>  
switch (<expression>) {  
case <case 1>: <Statements 1>; break;  
a multi-way decision  
that tests whether an  
expression matches one  
of a number of constant  
integer values, and  
case <case 2>: <Statements 2>; break;  
…
case <case N>: <Statements N>; break;  
[default: <Default>]  
branches accordingly  
}
20  
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