chapter2 constants, variables, and data types. 2.1 introduction in this chapter, we will discuss...
DESCRIPTION
Objective 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.TRANSCRIPT
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;