3_Data Type_Variables_Constants_Data Input.pdf

PRG 155 – Programming Fundamentals Using C 3. Variables Variable is a named storage location (memory location), that stores a value of a particular data type (Hock-Chuan). Declaration syntax: data_type variable_name; where data_type represents the variable data type variable_name is a...

PRG 155 – Programming Fundamentals Using C 3. Variables Variable is a named storage location (memory location), that stores a value of a particular data type (Hock-Chuan). Declaration syntax: data_type variable_name; where data_type represents the variable data type variable_name is a variable name Multiple variables of the same data type may be declared in the same statement where names are separate by commas. Example: int number1, number2, sum; Variables can be initiated in the declaration statement by using the assignment operator (=). Example: int number1 = 1; Important to remember:  Every variable must be declared before it is used.  Variable can only store a value of a specified data type.  A variable may take different values during the program execution.  Each declaration statement must end with semi-colon (;). Variable name Since the variable names are identifiers, the naming convention must follow the rules given for identifiers. 1 PRG 155 – Programming Fundamentals Using C Data types Data Types Basic User-defined Data (Primitive/Primary) Derived Data Types Types Data Types Character (char) Array Structure Integer (int) Pointer Union Single precision floating point Function Enumeration (float) Double precision floating point (double) No value available (void) 2 PRG 155 – Programming Fundamentals Using C “Primary Data Type.” n.d. Online Image. Studytonight. 23 Jan, 2017. http://www.studytonight.com/c/datatype-in-c.php Note: signed, unsigned, short, and long are type modifiers. Data Type Keyword Storage Value range size Character char 1 byte -128 to 127 or 0 to 255 Unsigned character unsigned char 1 byte 0 to 255 Signed character signed char 1 byte -128 to 127 Integer int 2 OR -32,768 to 32,767 OR 4 bytes -2,147,483,648 to 2,147,483,647 Unsigned integer unsigned int 2 OR 0 to 65,535 OR 4 bytes 0 to 4,294,967,295 Short integer short int 2 bytes -32,768 to 32,767 Unsigned short integer unsigned short int 2 bytes 0 to 65,535 Long integer long int 4 bytes -2,147,483,648 to 2,147,483,647 Unsigned long integer unsigned long int 4 bytes 0 to 4,294,967,295 Float float 4 bytes -1.2E-38 to 3.4E+38 Precision: 6 decimal places Double double 8 bytes 2.3E-308 to 1.7E+308 Precision: 15 decimal places Long double long double 10 bytes 3.4E-4932 to 1.1E+4932 Precision: 19 decimal places The sizes and ranges of different variable types are compiler dependent. To get the exact size of a data type, the operator sizeof() can be used. The expression sizeof(data_type) will return a number of bytes required to store a particular data type. 3 PRG 155 – Programming Fundamentals Using C Constants (Literals) A named memory location which holds a fixed value that cannot be modified by the program during its execution Types of constants:  Integer o Decimal – Example: 123 o Octal – Using prefix 0. Example: 0123 o Hexadecimal – Using prefix 0x or 0X. Example: 0x2A  Floating point – Examples: 123.45, -0.2E-2  Character o Examples: ‘A’, ‘1’, ‘&’ o Special Backslash character constants – Example: ‘\n’  String – Example: “Seneca” Defining Constants There are two ways to define a constant in C:  using #define preprocessor Examples: o #define PI 3.14 o #define NEWLINE ‘\n’  using const keyword Examples: o const int SIZE = 100; o const float PI = 3.14; o const char NEWLINE = ‘\n’; Example: #include #define SIZE 10 int main() { const float PI = 3.14; const char letter = 'A'; Output: printf("pi=%.2f\n", PI); pi=3.14 printf("Section: %c\n", letter); printf("size = 2 x %d = %d\n", SIZE, 2*SIZE); Section: A return 0; size = 2 x 10 = 20 } 4 PRG 155 – Programming Fundamentals Using C Function scanf() scanf() function reads data from the input device (usually keyboard) and store it in a variable. To use scanf() function, you will have to include header (same as for printf()). Syntax: scanf(“format_string”, &variable1, &variable2, …); where  format_string – Specifies the data type of each variable from the list. Common format specifiers: Data Type Format Specifier int %d float %f double %lf char %c string %s  Ampersand sign (&) – “Address of” operator o Tells scanf() where (in memory) to store the new value entered by the user o Missing & in scanf() is a common error; it leads to abnormal program termination. Example: int number; printf("Enter a number: "); //User prompted to enter a number scanf("%d", &number); After scanf() is called, the program waits for user to enter a value and press the “Enter” key. scanf() can be used to enter multiple values, of different or same data types, as shown in the example below: int age; float height; printf("Enter your age and height: "); scanf("%d%f", &age, &height); // %d is used for variable age, %f for height 5 PRG 155 – Programming Fundamentals Using C References  Tan, H.H., and T.B. D’Orazio. C Programming for Engineering & Computer Science. USA: WCB McGRaw-Hill. 1999. Print.  Hock-Chuan, Chua. C programming Tutorial. Programming notes, n.d. Web. 23 Jan, 2017.  Tutorialspoint.com. "C Data Types." Www.tutorialspoint.com. N.p., n.d. Web. 02 Mar. 2017..  Tutorialspoint.com. "C Constants and Literals." Www.tutorialspoint.com. N.p., n.d. Web. 02 Mar. 2017.. 6