Bahasa C : Struktur Program dan Tipe Datasi.ilkom.unsri.ac.id › wp-content › uploads › 2018...
Transcript of Bahasa C : Struktur Program dan Tipe Datasi.ilkom.unsri.ac.id › wp-content › uploads › 2018...
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Computer Science Department
Bahasa C : Struktur
Program dan Tipe Data
Knowledge:
Understand the complete structure and data type of C programs
Skill:
Edit, compile and execute C programs
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/* Task: This program calculates BMI */
#include
#define WEIGHT 60.0
#define HEIGHT 1.53
void main(void) {
float bmi;
bmi = WEIGHT / (HEIGHT * HEIGHT);
if (bmi > 0.0025)
printf(“\nYour BMI is %.2f. Need to lose weight! \n”, bmi);
}
TK1913-C Programming 2
Introduction
Resembles Algebraic
Expression
Augmented by certain
English keywords
eg. if , else, while
C is a High-level Language Can also be used at lower-level This flexibility allows it to be
used for SYSTEM
PROGRAMMING (eg.
Operating systems like
UNIX and WINDOWS)
APPLICATION
PROGRAMMING
(Billing System ? )
C has small instruction set,
though the actual
implementations include
extensive library functions
“myfunction.h”
C encourages users
to write additional
library
functions of their own
Finally, C programs are highly
portable.
They can be executed on different
platforms without having to be
recompiled (or with little modification)
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TK1913-C Programming 3
C Program Structure
Preprocessor
Instruction
void main (void)
{
}
Statement
Global Declaration
Local Declaration
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TK1913-C Programming 4
Example of C Program
#include
void main(void) {
printf(“Welcome to Fasilkom Unsri!”);
}
program
Main function
statement Preprocessor instruction
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TK1913-C Programming 5
Preprocess Instruction
2 types of preprocess instruction that are
normally used:
#include
#define
#include is used to include certain files into the
program. Those files need to be included
because they contain the necessary information
for compilation (e.g. stdio.h file contains
information about printf function)
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TK1913-C Programming 6
Preprocess Instruction #define is used to declare macro constants
Example:
#include
#define PI 3.141593
void main(void) {
float luas;
luas = PI * 7 * 7;
printf(“Luas %.2f:”, luas);
}
Macro constant
Before preprocess Example:
#include
#define PI 3.141593
void main(void) {
float luas;
luas = 3.141593 * 7 * 7;
printf(“Luas %.2f:”, luas);
}
After preprocess
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TK1913-C Programming 7
Main Function
Every C program must have a main
function, called main()
The execution of C program starts from
main() function
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TK1913-C Programming 8
Statement
„Sentence-like‟ action steps that are written in the
body of the function
In C, all statements must be ended with ; symbol
Example: A statement to display a string of characters on the screen by using printf() function
printf(“Welcome to Fasilkom Unsri”);
Output:
Welcome to Fasilkom Unsri
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TK1913-C Programming 9
Comment You could include comments in your program to ease
understanding
Comments will be ignored during compilation
A block of comment is labeled with /* (start) and */ (end)
compiler will ignore any text written after /* symbol till */
symbol is found
Nested comments (comment within comment) are not
allowed, for example:
/* my comment /* subcomment*/ my comment continues */
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TK1913-C Programming 10
Example of C Program
/* This program is to print Welcome to Fasilkom Unsri */
#include
void main() {
printf(“Welcome to\n”);
printf(“Fasilkom“);
printf(“Unsri\n”);
}
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TK1913-C Programming 11
Example of C Program
Welcome to
Fasilkom Unsri
What will the output be?
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TK1913-C Programming 12
Identifiers
Identifiers are:
Variable
Constant
Function
Others
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TK1913-C Programming 13
Identifiers
Syntax Rules:
Consist of only letters, digits and underscores
Cannot begin with a digit
Cannot use C reserved words
Try not to use/redefine C standard identifiers
What are C reserved words?
What are C standard
identifiers?
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TK1913-C Programming 14
C Reserved Word
A word that has special meaning in C
C Standard Identifier
A word having special meaning but may be
redefined (but is not recommended!!)
Examples of reserved word:
int, void, double, return Examples of standard identifiers:
printf, scanf
Identifiers
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TK1913-C Programming 15
Variable
A name associated with a memory
cell whose value can change
Needs to be declared:
variable_type variable_name;
Example: int x;
int entry_time, charge;
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TK1913-C Programming 16
Variable Types of variable:
Character: char
An individual character value – a letter, a digit or a
symbol (e.g. „A‟, „4‟, „*‟)
Integer: int
Whole numbers (e.g. +16, 568, -456)
Float: float
A real number which has a decimal point (e.g. 8.00,
3.1416)
High-level Float: double
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TK1913-C Programming 17
Variable
Variable Declaration:
Example 1:
char letter;
letter is a character-type variable
Example 2:
float matric;
matric is a ??? variable
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TK1913-C Programming 18
Variable
Example:
Calculate and display the price of a number of
apples if the quantity in kg and price per kg are
given.
•Input: quantity and price_per_kg
•Output: price
•Process: price = quantity * price_per_kg
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TK1913-C Programming 19
Variable
Example:
int quantity;
float price_per_kg;
float price;
Why did we
declare it as int?
Why did we
declare them as
float?
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TK1913-C Programming 20
Example:
int number1, number2;
number1 = 25;
number2 = 23;
number1 = number2;
…
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Variable - Value Assignment
number1 ?
number2 ?
25 23
23
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TK1913-C Programming 21
Variable - Value Assignment
Algorithm
variable expression
Syntax
variable = expression;
Rules
Expression‟s type must be the same as variable‟s type
Valid Example: Invalid Example:
int x; int y;
x = 12; y = 5.75;
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TK1913-C Programming 22
Variable - Value Assignment
Example:
int quantity;
float price_per_kg, price;
quantity = 5;
price_per_kg = 4.50;
price = quantity * price_per_kg;
…
How does this
program work?
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TK1913-C Programming 23
Example:
int quantity;
float price_per_kg, price;
quantity = 2;
price_per_kg = 4.50;
price = quantity * price_per_kg;
…
Variable - Value Assignment
quantity ?
price_per_kg ?
price ?
4.50
9.00
2
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TK1913-C Programming 24
Variable - Value Assignment
Example:
int number1, number2;
number1 = 25;
number2 = 23;
number1 = number2;
…
…
How does this
program
segment work?
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TK1913-C Programming 25
Constant
A value that will not change
Consists of:
Float (e.g. 2.3 0.255)
Integer (e.g. 3 67 -2)
Character(e.g. „z‟ „3‟ „$‟ „\n‟)
String (e.g. “UKM” “1” “5a”)
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TK1913-C Programming 26
Exercise
To practice what you‟ve
learned, try exercises on
Lab
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TK1913-C Programming 27
End of Lecture 4
What’s next? …INPUT AND OUTPUT on the way …
If you want to excel: • revise chapter 1 & 2
• practice programming skills for next week… Otherwise, you may watch tv, sleep etc. as a preparation for next week classes.