LAB 1 REPRESENTATION OF NUMBERS AND INTRODUCTION TO C

Transcription

1 LAB 1 REPRESENTATION OF NUMBERS AND INTRODUCTION TO C 1. LAB OBJECTIVE The objective of this lab is to review binary numbers and to review/introduce you to the C programming language and the MATLAB environment. Specifically, you will learn: How to use the Visual C++ editor in Microsoft Developer Studio for writing C programs How to compile and execute C programs in Developer Studio Basic C syntax The use of for loops The use of arrays Hexadecimal and binary number systems Plotting data in MATLAB 2. BACKGROUND 2.1. C Language Basics C will be used extensively throughout this class, and the first two weeks will be devoted specifically to the C language. Several good books on C are available and can be used to review the basic syntax of C as well as to study example programs: Brian W Kernighan, Dennis M Ritchie, The C Programming Language, Prentice Hall. Byron S Gottfried, Schaum s Outline of Theory and Problems of Programming in C, (Schaum s outline series), McGraw Hill. In addition, the course web site includes a tutorial on C. For Lab1, the following aspects of C will be emphasized: Declaring variables (integer, floating point, character) Basic math operations (+, -, *, /) Scanf and printf statements Loops ( for, while ) Arrays 2.2. Unary operators (++, --) The unary operators ++ and -- are shorthand notation for incrementing and decrementing variables.

2 (i++) is equivalent to i=i+1 (i--) is equivalent to i=i-1 The unary operators ++ and -- can appear either before or after a variable. The order can make a difference, for example: but notice that i = 1; a = i++; /* results in a = 1; i = 2 */ i = 1; a = ++i; /* results in a = 2; i = 2; */ Write a test program to try it yourself if you don t believe it. Writing test programs is often the most effective way of learning the subtleties of C syntax = operator a += b; is equivalent to a = a + b; Similarly, we can use -=, *= and /= operators Number Systems Computers and programs that use real-time data acquisition systems deal with binary numbers (1s and 0s, i.e. ON/OFF states), hence, we need to know how to represent numbers in binary (base-2) numbering systems. Instead of dealing directly with binary numbers, though, it is often more convenient to use hexadecimal (base-16) numbers. For example, we will use hexadecimal (hex) numbers when we address input/output (I/O) ports on the Sensoray card for reading and writing electrical signals in this course. The following sections outline procedures for converting from decimals to hex and for representing negative numbers in hex Converting Decimal Integers to Two s Complement Hexadecimal Integers Consider the following examples. Example 1: Convert the decimal number to hexadecimal.

3 Solution: Form the following table: Quotient Integer part Remainder 18435/ / / / Read the reminder column from bottom to top, i.e Therefore, 4803 is the hexadecimal two s complement representation of the decimal number In C, hexadecimal numbers are typically represented with a 0x in front of them. For example 4803 is written as: 0x4803. Note: This procedure also works when converting to other bases. For example, to convert to binary (base-2) divide by 2 instead of 16 in the quotient column above Representing Negative Decimal Integers This involves two steps. First find the hex equivalent of the magnitude of the number. Then find its two s complement. The procedure for finding the two s complement of a number is explained below using an example. Example 2: Convert the decimal number to hexadecimal. Solution: First, find the hexadecimal value of , then take two s complement of that value. The result is the hexadecimal value of Note: Taking the two s complement of a number gives the negative of that number. From Example 1, the hexadecimal value of is 0x4803. Now, take the two s complement of 0x4803. Convert the hexadecimal number to binary. 0x4803 = ( ) in binary Complement the binary number by changing the 1 s to 0 s and the 0 s to 1 s: Complement of ( ) is ( )

4 Add one to the complement: ( ) + 1 ( ) Convert back to hexadecimal. ( ) = 0xB7FD 0xB7FD is the two s complement of 0x4803. Thus, 0xB7FD = As a check, verify that 0x xB7FD equals zero: 0x xB7FD + (-18435) 0x0000 0x00000 When adding two s complement numbers, ignore the remainder of the most significant digit if there is one, i.e., ignore the overflow bit. The example below shows a faster method of obtaining the two s complement of a hexadecimal number: What is the two s complement of 0xB7FD? Solution: Subtract each hexadecimal digit from B F - D Add one: 0x x4803 This is the same result as above Declaring Hex Numbers in C Example: #include <stdio.h> main() { int a = 0x4803; int b = 0xb7fd; int c; c = a + b; printf( \n A =%x, B =%x, C =%x \n,a,b,c);

5 The value of c should be zero in the output. Here the %x format tells the printf statement to print hexadecimal numbers Loops and if statements Review the online C tutorial paying particular attention to the following concepts if statement for loops while statement array declaration function declaration Adding comments to the program 2.9. break statement The break statement can be used to exit from loops (for, while). The following two programs produce identical results /* First program */ #include <stdio.h> #include <conio.h> /* conio declares console i/o functions like getch */ void main() { char a= a ; while(a!= 'q') { a = getch(); printf("you typed in %c\n", a); /* Second program */ #include <stdio.h> #include <conio.h> /* conio declares console i/o functions like getch */ void main() { char a= a ; while(1) {

6 a = getch(); printf("you typed in %c\n", a); if(a == 'q') break; continue statement The continue statement is used to bypass the remainder of the current pass through a loop. The loop does not terminate when a continue statement is encountered. Rather, the remaining loop statements are skipped and the computation proceeds to the next pass through the loop. For example, consider a program that prompts a user for an input and calculates the square root of the number. Whenever a negative number is encountered we want to ignore the input. #include <stdio.h> #include <math.h> /* declares math functions */ void main() { int i; double x,y; for(i=0; i < 10; i++) { printf("\n Enter a positive number: "); scanf("%lf",&x); if (x < 0.0) continue; /* ignore this dope s input */ y = sqrt(x); printf( \nthe square root of %f is %f\n,x,y); /* end of for */ /* end of main */ Arrays Review the lecture slides and the online C tutorial paying particular attention to the declaration and use of arrays. 3. PRELAB 1. Read the lab handout and any additional readings listed in the handout. 2. Write a program to convert temperature reading in degree Celsius to degree Fahrenheit (F=(9/5)C + 32). Take the Celsius value as the input from user and print out the Fahrenheit value to the screen. 4. Perform the following calculations (written hand in required). Calculate the sum in hexadecimal numbers. 0x x0009 0x x0079 0x x54BF 0x x4A05????

7 5. Convert the augends and addends of the above problem to binary, then calculate the sum for each problem. 6. Convert the augends and addends of the above problems to decimal, then calculate the sum for each problem. 7. Write a program that uses nested "for" loops to sort an array of integer numbers. Input = [ ]; Output = [ ]; 4. LAB PROCEDURE Microsoft Developer Studio will be used for creating and compiling C programs. More specifically, the Visual C++ Integrated Development Environment (IDE), a part of Developer Studio, will be used for program development (C++ will not be covered in this class). The IDE provides an editor where source code can be written, compiled and run. The IDE is a useful tool to learn, because Microsoft intends to support all future Windows programming languages within this environment. To get started with the editor follow the guidelines below. Creating a new project in Visual C++: Open the program by clicking on the Visual Studio shortcut on the Desktop or through the start menu of Windows (Start All programs etc.) When the program is opened, Click on File New Project. From the dialog box which opens up select Visual C++ Projects Win 32 under the Project Types Window on the left hand side of the dialog box. From the Templates window on the right, select Win32 Console Project. Now you should give a name to the project. Use reasonable names to avoid confusion in the future. For the defining the Location click Browse and choose a directory within your protected disk subdirectory area on drive Z:, which corresponds to the file server for this class. For example, using Windows Explorer you might want to create a subdirectory called Z:\userid\projects. If you choose this as the location of your workspace, then the directory Z:\userid\projects\lab1 will be created along with three workspace files required by Developer Studio. Click OK. This opens a Win32 Application Wizard dialog box. Click on Application Settings tab and check the Empty Project checkbox. Click Finish. A new project with the name that you specified opens. Creating a new C source file under a project: To add a new source file to your project select from the menu: File New File. On the dialog box that opens up select Visual C++ under the categories window and select C++ File under the templates window that is on the right hand side. Click Open Now to save the file from the menu select : File Save As and then from the Save As dialog box locate you project directory under Shared Documents students YOUR

8 NAME PROJECT NAME(or for future labs Z:\userid\projects\project name). You can give any name to the source file while saving as long as its extension is left as.cpp. Now you have to add this source file to the project. To do this from the Solution Explorer window under your project name, right click on Source Files and on the pop-up menu select Add Add existing item. Then locate the.cpp file you just saved and click open. 1. Now you are ready to start keying in your source code. Enter this program: #include <stdio.h> main() { printf( \n Hello World\n ); Save the file. Then try to compile and run this program. Compiling and running options are available under the BUILD tool bar. (note: as you become more proficient at the IDE, you will want to learn how to use the task bar or hotkey options to speed program development.) The \n statement inside the printf is called a newline character. Basically a newline is printed on the screen. Try the program without the \n in the printf statement and see the output. 2. Implement and debug the Celsius to Fahrenheit conversion program that you have written in your prelab. 3. Write a program to check the addition of hexadecimal numbers that you have done in the prelab. (refer to the example program given under the number systems section given in this handout). 4. Implement the sorting algorithm program. 5. Refer to the MATLAB handout given on the web site. Open the MATLAB window by double clicking on the MATLAB icon. Try out the simple math operations suggested in the MATLAB handout. PLOTTING GRAPHS IN MATLAB: Write a m-file that does the following 1) Creates a vector t with elements of t ranging from 0 to 5 seconds at time intervals of 0.1 seconds. 2) Creates a vector y which has elements that are a function of the elements of the vector t. a) The vector y is a sinusoid with an amplitude of 1 and a frequency of 1 Hz. b) The vector y is a sinusoid with an amplitude of 0.5 and a cycle time (period) of 0.1 seconds. 3) Plots y as a function of t for both (2a) and (2b). In each case, what is the frequency of the signal y (t) in radians/sec?

9 Show your working programs to your TA. Note on Projects and Workspaces When writing complicated programs that require several subroutines, it is a good idea to split up the source code into multiple files instead of placing everything inside a single file. In such a situation we want to have all files related to the main task to be easily accessible. As some software projects become so large, it may be too cumbersome to store all files related to a main task in the same directory. This is where the concept of a project helps. Basically it is a tool for handling multiple file programs. All files related to a particular task could be added to a project. The files still continue to exist in different directories, but the project provides a link for easily accessing these files. This collection of related files is called a project. For this course, a single directory for the project should suffice, though you may want to use multiple files. However, feel free to organize things differently if you feel the need. You will understand the importance of the concept of a project as we proceed to more complicated programs in this course. We still need to create a project to work on files since VC++ expects you to create a project even for single file programs. 5. POSTLAB AND LAB REPORT 1. Represent the decimal integer 11,304 as a two s complement hexadecimal integer. Show the steps followed clearly. 2. Submit a commented copy of your sorting program in task Submit a copy of your Matlab code, plots and answer to question 3 in task Come prepared with Prelab 2 for Lab 2.