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2.1 Introduction2.1 Introduction• In this chapter, we will discuss
– constants (integer, real, character, string, enum) ,symbolic constants
– Variables (name, declare, assign) – Fundamental data type ( int, float,
double, char, void)
ObjectiveObjective• To be able to distinguish the
constants of different data type • To be able to name,
declare , initialize and assign values to variables
• To become familiar with fundamental data types.
2.1 Character set2.1 Character set• Letters
– uppercase A…Z– lowercase a…z
• Digits :All decimal digits 0…9 • Special characters
– Table2.1 on page23• White spaces
2.4 Keywords and Identifiers 2.4 Keywords and Identifiers • Keywords
– Table2.3 on page24– Must in lowercase
• Identifiers– User-defined names– Consist of letters, underscore(_), and
digits– First character must not be digit– Can’t use a keyword– Can’t contain white space
2.4 Keywords and Identifiers2.4 Keywords and Identifiers• Which of the following are valid
identifiers• Max first_name n1/n2• 3row double _34• Boy num girl-num
2.7 Data Types2.7 Data Types• Primary( fundamental) data types
– Integer– Floating point ( float and double )– Character– Void
• Fig.2.4 on page31
2.7 Data Types2.7 Data Types• Integer
– signed /unsigned• int• short int• long int
• Floating point – float– double– long double
• Character– signed / unsigned
• void
2.7 Data Types2.7 Data Types• Size and range of basic data types• Table 2.7 on page31• Table 2.8 on page32
Integer constantsInteger constants• Decimal integer
– Consist of 0 through 9, +, -• Octal integer
– Consist of 0 through 7, with a leading 0• Hexadecimal integer
– Consist of 0 to 9, and a through f preceded by 0x or 0X
Integer constantInteger constant• The largest integer value is machine-
dependent• Qualifiers
– U or u: unsigned integer– l or L: long integer – UL or ul: unsigned long integer– Short integer
Integer constantInteger constant• Example2.1 Representation of integer constants on
a 16-bit computer.
#include<stdio.h>main(){
printf("Integer values\n\n");printf("%d %d %d\n",32767,32767+1,32767+10);printf("\n");printf("Long integer values\n\n");printf("%ld %ld %ld\n",32767L,32767+1L, 32767+10L);
}
Real constant (double)Real constant (double)• (1) decimal point
– Consist of 0 through 9, . ,+ , -– 3.14159, .94 , -.58 , +1.234
• (2)Exponential notationmantissa e exponent
– .56e3 2.3e-3 -2.3E-3– The exponent must be an integer number
• Suffixes f or F indicate a float constant• L or l indicate a long double• “Default values of constants” on page35
• Floating-Point Round-off Errors • Take a number, add 1 to it, and
subtract the original number. What do you get? You get 1. A floating-point calculation, may give another answer:
Character constantCharacter constant• A character enclosed within ‘ ’– ‘6’ ‘=‘ ‘;’ ‘ ‘– Character constants have integer
values, For example– ‘a’ and 97– ‘0’ and 48
• Backslash character constants– Table2.5 on page28– ‘\ooo’ and ‘\xhh’
String constantsString constants• a sequence of characters enclosed in “ ”, for example– “hello” “34” “+()” “x” “\n”
• “x” and ’x’
2.6 variables2.6 variables• A variable is data name that may be
used to store a data value.– Variable names correspond to locations
in the computer's memory– Every variable has a name, a type, a
size and a value– Whenever a new value is placed into a
variable, it replaces (and destroys) the previous value
– Reading variables from memory does not change them
2.8 Declaration of variables2.8 Declaration of variables• The declaration of variables must be
done before they are used.• declaration form
data-type v1,v2,…,vn;• for example
– int count;– float sum;– double ratio;– char ch;
Initialization of variablesInitialization of variables• To initialize a variable means to
assign it a starting, or initial, value.• In C, this can be done as part of the
declaration. • char ch=‘ ’; • int cows = 32,• int dogs, cats = 94;
2.10 Assignment statement2.10 Assignment statement• values can be assigned to variables
using the assignment operator = as
variable_name=value;
User-defined type declarationUser-defined type declaration• the keyword “typedef” is used to
rename an existing data type.typedef type identifier;
• for example– typedef int integer;– typedef float real;– real sum1, sum2;– integer count;