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More Syntax 1 ConstantConstant 2 Interactive Input 3 Today’s Overview 3
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SCCS200: INTERACTIVE INPUT
Lect. Napat Amphaiphan
Overview (Midterm)Midterm Examination
30 %
Data Type,Declaration,
Display
InteractiveInput Selection Repetition
Analyze
ProblemSolving
intfloatdoublechar
printf()
scanf()if…elseswitch…case
while statementfor statementdo-while statement
3
• More Syntax1
• Constant2
• Interactive Input3
Today’s Overview
Identifiers
• Identifiers in C consist of three types:– Reserved words– Standard identifiers– Programmer-created identifiers
IdentifiersReserved Word
IdentifiersStandard Identifiers
IdentifiersProgrammer-created identifiers
• Programmer-created identifiers:
selected by the programmer
– Also called programmer-created names
– Used for naming data and functions
– Must conform to C’s identifier rules
– Can be any combination of letters, digits, or underscores (_) subject to the following
rules:
• First character must be a letter or underscore (_)
• Only letters, digits, or underscores may follow the initial character
• Blank spaces are not allowed
• Cannot be a reserved word
FORMATTED OUTPUT- HOW TO FORMAT THE OUTPUT PRINT BY PRINTF FUNCTION (I/O)
Formatted Output
• Field width specifiers– to control the format of numbers
• Example of integer numbers
printf(“The sum of%3d and%4d is%5d.”, 6, 15, 21);
The sum of __6 and __15 is ___21.
– Each integer is right-justified within the specified field
Formatted Output (cont.)
Formatted Floating Point Numbers
• Require two field width specifiers
– determines the total display width, including the decimal point
– determines how many digits are printed to the right of the decimal
point
• Example
printf(“|%10.3f|”, 25.67); |____25.670|
The bar character (|) is used to mark the beginning and end of the display field
Formatted Output (cont.) Left Justification
to force the output to left-justify uses a minus sign (-) format modifier Example
printf(“|%-10d|”,59);
|59________|
Formatted Output (cont.) Explicit Sign Display
to force both positive and negative signs to be displayed uses a plus (+) format modifier Example
printf(“|%+10d|”,59);
printf(“|%-+10d|”,59);
|_______+59|
|+59_______|
Assignment Variations
Assignment Variations (cont.)
• Assignment expressions like sum = sum + 10 can be written using the following operators:– += -= *= /= %=
• sum = sum + 10 can be written as sum += 10• price *= rate is equivalent to price = price * rate
• price *= rate + 1 is equivalent to price = price * (rate + 1)
Mathematical Library Functions
Must include #include <math.h>
Mathematical Library Functions (cont.)
Symbolic Constants
• C allows you to define the value once by equating
the number to a symbolic name– #define SALESTAX 0.05
– #define PI 3.1416
– Also called symbolic constants and named constants
Syntax: #define identifier value
INTERACTIVE INPUT- FOR THE PAST PROBLEM, YOU ‘FIX’ VALUE OF EACH VARIABLE IN THE CODE.
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ANY CHANGE IN THE VARIABLE VALUE, YOU NEED TO OPEN YOUR CODE AND RE-WRITTEN IT !!!
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“I WANT THE USER TO INSERT THE VALUE WHILE KEYBOARD”
Company Logo
Interactive Input
• scanf() is used to enter data into a program
while it is executing; the value is stored in a
variable
– It requires a control string as the first argument
inside the function name parentheses
Interactive Input (cont.)
• scanf() will receive inputs from the user via keyboard, the user must press ‘enter’ to tag the end of data.
• scanf() requires that a list of variable addresses follow the control string
Syntax: scanf("%d", &num1);
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Interactive Input (cont.)
• Syntax: scanf(control, argument-list) ;
1. argument-list: a variable to keep an input value (must be preceded with ‘&’).
More than 1 value, must be used with ‘,’
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Interactive Input (cont.)
2. Control: a format as in the follow table, it must be preceded with ‘%’.
Symbol Format
%d Integer
%f Float
%c Character
%s Text
%u Unsigned integer
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Interactive Input (DEMO)
• EX1. Using scanf() with %d– scanf ("%d", &x);
• EX2. Using scanf() with 2 numbers using %d (integer)– scanf ("%d,%d",&x1,&x2);
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Interactive Input (DEMO)
• EX3. Using scanf() with format %d with a text massage to describe input (a prompt)– printf("Input first number:");– scanf("%d",&x1)
• EX4. Using scanf() to receive 3 characters– scanf("%c%c%c",&i, &j, &k);
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Interactive Input (DEMO)
• EX5. Using scanf () to receive a text massage to describe input– printf("Enter your name:\n");
scanf("%s",&name);
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