Data Structures and Programming with C++

Transcription

1 Data Structures and Programming with C++ By Dr. Atul Kumar Dwivedi ETC, BIT, Durg UNIT-I B. E., V Semester

2 Outline Identifiers in C++ Data types Functions in C++ Return values in functions Quiz Lab exercises 2

3 Identifiers C++ identifier is a name used to identify a variable, function, class, module, filename or any other user-defined item. It should starts with a letter A to Z or a to z or an underscore (_) followed by more letters, underscores, and digits (0 to 9). Identifier do not allow punctuation characters such $, and % within identifiers. Identifier should not contain space character Identifier should not start with a number C++ is a case-sensitive programming language. Thus, MYPROGRAM, myprogram and Myprogram are three different identifiers in C++. 3

4 Data types Variables are reserved memory locations to store values. This means that when you declare a variable in C++, you reserve some space in memory. Based on the data type of a variable, the operating system allocates memory. Data types includes character, integer, floating point, double floating point, boolean etc. Type Char Integer Float Double Memory 1 byte 2 byte 4 byte 8 byte Refer myp09.cpp for example on memory requirements of data types 4

5 Functions C++ functions work the same way as in C. A program will be executing statements sequentially inside one function when it encounters a function call. A function call is an expression that tells the CPU to interrupt the current function and execute another function. Example: refer program myp12.cpp 5

6 Return values When you write your own functions, you get to decide whether a given function will return a value to the caller or not. This is done by setting the return type of the function in the function s definition. The return type is the type declared before the function name. Note that the return type does not indicate what specific value will be returned. It only indicates what type of value will be returned. Example: refer program myp13.cpp 6

7 Functions in different files Refer myp07.cpp and myp08.cpp and add. cpp details for more Compile myp08.cpp and add.cpp simultaneously to create object file with name sap.o Command is g++ myp07.cpp add.cpp subs.cpp o sap.o 7

8 Variable Scope A scope is a region of the program and broadly speaking there are three places, where variables can be declared Inside a function or a block which is called local variables, In the definition of function parameters which is called formal parameters. Outside of all functions which is called global variables. Local Variables Variables that are declared inside a function or block are local variables. They can be used only by statements that are inside that function or block of code. (refer program myp10.cpp) Global variables A global variable can be accessed by any function. That is, a global variable is available for use throughout your entire program after its declaration. (refer program myp11.cpp) 8

9 Quiz question 1. What is the difference between local variables and global variables. 2. Tell weather the language C++ is case sensitive or not? 3. What is the importance of sizeoff() keyword in C++; 4. Define function? 5. What are the advantages of using functions in C++; 9

10 Lab Exercise 1. Write a function to add two numbers. Input: The input consist of two numbers (integers) entered by user separated by a space in main function. Output: Sum is calculated in the called function and output should be displayed in main function. The output should contain a single integer which is the sum of the two input integers. 2. Write a program to find half of the factorial of the number Input: input is a integer number given by the user in the main function Output: The value of the factorial returned back to the main program. Display half value of the factorial in the main program 10

11 Lab Exercise (contd ) 3. Write four different function for addition and subtraction, of two numbers. Keep the codes in different files. Input: The input consist of two numbers (integers) entered by user separated by a space in main function. Output: Sum is calculated in the called function and output should stored in the global variable. The output should contain a single integer which is the sum of the two input integers. 4. Convert the C program given in labex2_4.txt into C++ code and write the output of the program for 11

12 Dr. Atul Kumar Dwivedi, BIT Durg, (India) atuldwivedi@live.in 8/11/