VariableWhy Need VariableHow – DeclarationDeclaration of VariablesBasic Types of VariablesVariable NamesVariable Names – cont.int: integer VariablesOperations for int typeDisplay Integer Variables – IDisplay Integer Variables – IIint: integer Variables – Special Case Iint: integer Variables – Special Case IIExample - IExample – IIfloat: single-precision Variablesfloat Variables - IIfloat Variables - IIIOperations for float typeExample – Idouble: double-precision Variableschar: character VariablesSlide 23_Bool: Boolean TypeFinish the CodeSpecial variable typesSummary of Data TypeSummary of Data Type – cont.Assignment OperatorsUnary OperatorsArithmetic OperatorsOperator PrecedenceVariable•Symbol represents a place to store information–name–value–memory space–Example: somebody’s age•An integer variable age;•age = 20;•Contrasted with constants–No change in constants Computer memoryage20Why Need Variable•Remember a value–Requests a value from the user–Results from calculation–Example:•int v1, v2, sum;•v1 = 50;•v2 = 30;•sum = v1 + v2;* = means assign the value as•Provide a way to access your computer's memory Computer memoryv1 50v2 30sum 80How – Declaration•A variable must be declared before it can be used. –Tell the computer that you need to store a number in a variable •Mostly declared at the start of each function. •Declaration format:type name = initial_value;type name1 = initial_value1, name2 = initial_value2, …;–It is not required to put initial value in declarationDeclaration of Variables type name = initial_value;type name1 = initial_value1, name2 = initial_value2, …;{int v1, v2, sum;v1 = 50;v2 = 30;sum = v1 + v2;}{int v1= 50, v2 = 30, sum;sum = v1 + v2;}Basic Types of Variables •int –integer•float –single-precision floating point •double–double-precision floating point •char –one byte character •_Bool–BooleanVariable Names•Contain one or more characters, –A-Z, a-z –0-9 –_•Must start with a non-digit character–A-Z, a-z–_Variable Names – cont.•Cannot be C's keywords–int, main, while, etc•Limitation–Maximum of 63 characters for a variable name•Sometimes 31•or 8 in very old C•Case sensitive: upper and lower case characters are different•floating•int•Int•main3•4yiint: integer Variables•For integral values only10, -5, 1000–no fraction10.2 –no commas12,000•Ranges–Machine dependent•Minimum: 16 digits•32 bits of storage on grove.ufl.edu (usual)–Signed: −2,147,483,648 to +2,147,483,647–Unsigned: 0 to +4,294,967,295 •Maybe 64 on othersOperations for int type•Declarationint x, y, z;•Assignment–y = 10;–z = 5;•Calculation–Plus: + •x = y + z;–Minus: -•x = y – z;–Muliply: *•x = y * z;–Divide: /•x = y / z;–Modulus •x = y % z;result of y/z will be truncatedDisplay Integer Variables – I#include <stdio.h> Preprocessor: interact with input/output of your computer Start point of the program int main() Start and finish of function{ } Printing results int value1, value2, sum;Finish and return value 0 return 0; value1 = 50; value2 = 30; sum = value1 + value2; printf(“The sum of 50 and 30 is %i\n“, sum); Declear VariablesDefine ValuesSummation Print the value of an integer variableDisplay Integer Variables – II#include <stdio.h> int main() { int value1, value2, sum; value1 = 50; value2 = 30; sum = value1 + value2; return 0; } printf(“The sum of %i and %i is %i\n“, value1, value2, sum);int: integer Variables – Special Case IStarting with digit “0”–Octal notation. Base 8, not 10•0,1,2,3,4,5,6,70177 = 1*64 + 7*8 + 7 = 1270256 = ?–Display•%i – print out the decimal value •%o – print out the octal value •%#o – print out the octal value, starting with 0int: integer Variables – Special Case IIStarting with digit “0x”–Hexadecimal notation. Based 16, not 10•0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F0x177 = 1*256 + 7*16 + 7 = 3750xAF = ?0x2AF = ?–Display•%i – print out the decimal value •%x – print out the hexadecimal value •%#x – print out the hexadecimal value, starting with 0Example - I#include <stdio.h>int main(){ int a, b, c, d; a = 10; b = 20; c = 0177; d = 0xAF; printf(“The four numbers are %i, %i, %#o, %#x\n”, a, b, c, d); printf(“The four decimal numbers are %i, %i, %i, %i\n”, a, b, c, d);}Example – II#include <stdio.h>int main(){ int a, b, c, f; a = 10; b = 20; c = 0177; f = a/b; printf(“%i / %i = %i\n”, a, b, f); f = b/a; printf(“%i / %i = %i\n”, b, a, f); f = c/a; printf(“%i / %i = %i\n”, c, a, f);}float: single-precision Variables•For values containing decimal3., 125.8, -0.1–Scientific notation2.25e-3 = 2.25 * 10-3 = 0.00225•Use e or E for exponent–no commasfloat Variables - II•Ranges –IEEE floating-point standard•e = 8, f = 23•±3.4×1038float Variables - III•Display–%f – print out the decimal value –%e – print out the scientific notation–%g – let printf decide the format•-4 < value of exponent < 5: %f format•Otherwise: %e formatOperations for float type•Declarationfloat x, y, z;•Assignment–y = 10.00;–z = 5.8;•Calculation–Plus: + •x = y + z;–Minus: -•x = y – z;–Muliply: *•x = y * z;–Divide: /•x = y / z;result of y/z will NOT be truncatedExample – I#include <stdio.h>int main(){ int a, b, c; float f; a = 10; b = 20; c = a/b; printf(“%i / %i = %i\n”, a, b, c); f = a/b; printf(“%i / %i = %f\n”, a, b, f);}double: double-precision Variables•Similar to float–More storage space (IEEE floating-point standard)•float variables: e+f+1 = 32•double variables: e+f+1 = 64–Ranges•±1.79769×10308 •Same display method as float•Operation similar as floatchar: character Variables•For single character–Enclosing the character within a pair of ‘ ’•‘a’•‘;’•‘P’•‘\n’•‘1’•Display–%cExample – II#include <stdio.h>int main(){ int a, b, f; char c; a = 36; b = 52; c = ‘a’; printf(“The three numbers are %i , %i, %i\n”, a, b, c); printf(“The three characters are %c , %c, %c\n”, a, b, c);}_Bool: Boolean Type•For boolean–0/1 –Normally means false/true •Display–%iFinish the Code#include <stdio.h>int main(void){ int integerVar = 100; float floatingVar = 331.79; double doubleVar = 8.44e+11;