computer science department ftsm variables and constants knowledge: understand the concept of...
TRANSCRIPT
Computer Science Department FTSMFTSM
Variables and ConstantsVariables and Constants
Knowledge:Understand the concept of storage location representation as identifiers
Skill:Identify and define data types in C programs
TK1913-C ProgrammingTK1913-C Programming 22
IntroductionIntroductionConsider the following example:
#include <stdio.h>
void main() {
printf(“Welcome to UKM\n”);
}
#include <stdio.h>
void main() {
printf(“Welcome to UKM\n”);
}
Let’s recap…Let’s recap…
Which one is the preprocessor Which one is the preprocessor instruction?instruction?
Which one is the main Which one is the main function?function?
TK1913-C ProgrammingTK1913-C Programming 33
C Program StructureC Program StructurePreprocessor Instruction
Pengisytiharan globl
void main (void){
}
Pengisytiharan setempat
Statement
Global Declaration
Local Declaration
Still remember Still remember this diagram?this diagram?
TK1913-C ProgrammingTK1913-C Programming 44
IdentifiersIdentifiers
Identifiers are:
Variable
Constant
Function
Others
TK1913-C ProgrammingTK1913-C Programming 55
Identifiers 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 identifiersWhat are C What are C
reserved words?reserved words?What are C standard What are C standard
identifiers?identifiers?
TK1913-C ProgrammingTK1913-C Programming 66
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, returnint, void, double, return
Examples of standard identifiers:printf, scanfprintf, scanf
Examples of reserved word:int, void, double, returnint, void, double, return
Examples of standard identifiers:printf, scanfprintf, scanf
Identifiers Identifiers
TK1913-C ProgrammingTK1913-C Programming 77
Variable Variable A name associated with a memory
cell whose value can change
Needs to be declared:
variable_type variable_name;variable_type variable_name;
Example: int x;int x; int entry_time, charge;int entry_time, charge;
Example: int x;int x; int entry_time, charge;int entry_time, charge;
TK1913-C ProgrammingTK1913-C Programming 88
VariableVariableTypes of variable: Character: charchar
An individual character value – a letter, a digit or a symbol (e.g. ‘A’, ‘4’, ‘*’)
Integer: intint Whole numbers (e.g. +16, 568, -456)
Float: floatfloat A real number which has a decimal point (e.g. 8.00,
3.1416)
High-level Float: doubledouble
TK1913-C ProgrammingTK1913-C Programming 99
VariableVariable
Variable Declaration:
Example 1:
char letter;char letter;
letterletter is a character-type variable
Example 1:
char letter;char letter;
letterletter is a character-type variable
Example 2:
float matric;float matric;
matricmatric is a ??? variable
Example 2:
float matric;float matric;
matricmatric is a ??? variable
TK1913-C ProgrammingTK1913-C Programming 1010
VariableVariable
Example:Calculate and display the price of a number of apples if the quantity in kg and price per kg are given.
•Input: quantityquantity and price_per_kgprice_per_kg
•Output: priceprice
•Process: priceprice = quantityquantity * price_per_kgprice_per_kg
Example:Calculate and display the price of a number of apples if the quantity in kg and price per kg are given.
•Input: quantityquantity and price_per_kgprice_per_kg
•Output: priceprice
•Process: priceprice = quantityquantity * price_per_kgprice_per_kg
TK1913-C ProgrammingTK1913-C Programming 1111
VariableVariable
Example:
int quantity;int quantity;
float price_per_kg;float price_per_kg;
float price;float price;
Example:
int quantity;int quantity;
float price_per_kg;float price_per_kg;
float price;float price;
Why did we Why did we declare it as declare it as intint??
Why did we Why did we declare them as declare them as
floatfloat??
TK1913-C ProgrammingTK1913-C Programming 1212
Example:int number1, number2;
number1 = 25;number2 = 23;number1 = number2;……
Example:int number1, number2;
number1 = 25;number2 = 23;number1 = number2;……
Variable - Value AssignmentVariable - Value Assignment
number1 ?
number2 ?
2523
23
TK1913-C ProgrammingTK1913-C Programming 1313
Variable - Value AssignmentVariable - Value AssignmentAlgorithm
variable variable expression expression Syntax
variable = expression;variable = expression;
RulesExpression’s type must be the same as variable’s type
Valid Example: Invalid Example:int x; int x; int y;int y;x = 12;x = 12; y = 5.75;y = 5.75;
Valid Example: Invalid Example:int x; int x; int y;int y;x = 12;x = 12; y = 5.75;y = 5.75;
TK1913-C ProgrammingTK1913-C Programming 1414
Variable - Value AssignmentVariable - Value Assignment
Example:int quantity;float price_per_kg, price;
quantity = 5;price_per_kg = 4.50;price = quantity * price_per_kg;…
Example:int quantity;float price_per_kg, price;
quantity = 5;price_per_kg = 4.50;price = quantity * price_per_kg;…
How does this How does this program work?program work?
TK1913-C ProgrammingTK1913-C Programming 1515
Example:int quantity;float price_per_kg, price;
quantity = 2;price_per_kg = 4.50;price = quantity * price_per_kg;…
Example:int quantity;float price_per_kg, price;
quantity = 2;price_per_kg = 4.50;price = quantity * price_per_kg;…
Variable - Value AssignmentVariable - Value Assignment
quantity ?
price_per_kg ?
price ?
4.50
9.00
2
TK1913-C ProgrammingTK1913-C Programming 1616
Variable - Value AssignmentVariable - Value Assignment
Example:int number1, number2;
number1 = 25;number2 = 23;number1 = number2;……
Example:int number1, number2;
number1 = 25;number2 = 23;number1 = number2;……
How does this How does this program program
segment work?segment work?
TK1913-C ProgrammingTK1913-C Programming 1717
ConstantConstant
A value that will not change
Consists of: Float (e.g. 2.3 2.73F 1.2e-5) Integer (e.g. 3 67 -2) Character(e.g. ‘z’ ‘3’ ‘$’ ‘\n’) String (e.g. “UKM” “1” “5a”)
TK1913-C ProgrammingTK1913-C Programming 1818
ExerciseExerciseTo practice what you’ve learned, try exercises on page 83 (Latih Diri) from Pengaturcaraan C
TK1913-C ProgrammingTK1913-C Programming 1919
End of Lecture 4End of Lecture 4
What’s next?What’s next? …INPUT …INPUT AND OUTPUTAND OUTPUT on the way on the way … …
If you want to excel:If you want to excel:• revise chapter 4revise chapter 4• read chapter 5 & 6 for next weekread chapter 5 & 6 for next week… … Otherwise, you may watch tv, sleep etc. as a Otherwise, you may watch tv, sleep etc. as a preparation for next week classes.preparation for next week classes.