Assignment 3: Binary numbers, data types and C Programs Due 11:59pm Monday 26th March 2018

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1 Assignment 3: Binary numbers, data types and C Programs Due 11:59pm Monday 26th March 2018 Objectives: Using binary numbers variable declarations variable types writing simple C programs Marks for the Assignment Parts of the Assignment: 1. A Core part, which involves programming in C to perform simple tasks using basic concepts and constructs, 2. A Completion part, which extends the Core part and involves more difficult thinking and may cover additional concepts, 3. A Challenge part, which usually involves substantially more difficult programming and problem solving. Successfully performing of all the Core tasks will enable you to get awarded up to 65% of the lab marks. Successfully performing all the Completion tasks enables you to be awarded a maximum of 80%, and the Challenge tasks can take you up to 100%. Actual questions are boxed. 1

2 1 Binary numbers Core 1 Convert the 4-bit binary number 1011 into its decimal form. Be sure to show your working. Core 2 Convert decimal 13 into 4-bit binary. Be sure to show your working. Core 3 Bit-shift 1011 one bit to the right. Because we are working in 4-bit binary your answer should contain only 4 bits. What is the decimal equivalent of this bit shifted number? Be sure to show your working. You should fill the vacated bit with a 0. Core 4 Bit-shift 1011 one bit to the left. Because we are working in 4-bit binary your answer should contain only 4 bits. What is the decimal equivalent of this bit shifted number? Be sure to show your working. You should fill the vacated bit with a 0. 2 C++ and Geany C++ is a language that can work with numbers in binary format and perform other low-level machine code commands, unlike some other high level languages (e.g. Java or Python). You will use C++ for much of your work in ENGR101 and it features heavily in the core code for many operating systems. C++ is a complied language. We will initially use an Integrated Delopement Environment(IDE), Geany, to make the compilation and execution of your code simpler. Launch Geany from your ECS machine (under the Development heading in the Start Menu). Core 5 What (qualitatively) does compiling do to C++ or Java code? necessary? Why is it Type in the following code for a simple C++ program into a new Geany page, save it with the title Ex1.cpp. Remember the folder(directory) you used. Open Dolphin file manager (System >Dolphin) and navigate to this folder. Check it s contents. In Geany click compile. Check contents of the folder now. In Geany click build. Check folder again. Can you see more files appearing in 2

3 the folder? Click execute in the Geany toolbar to run your code. Also rightclick in Dolphin window and select (Actions >Open Terminal Here). Konsole will open. Type Ex1 (or whatever you called your program but without.cpp extension). Listing 1: Ex1.cpp // Comment : This is the Hello Student Program. // this loads a standard input output library // this is the main method of C ++ programs printf (" Hello Student "); return 0; // This ends the C ++ main method. Core 6 Take a screen shot of the output of your code and include it in your report. Note that the output of your code is everything that comes before Process returned... Press ENTER to continue Core 7 What is extension for machine code (executable) file in Linux? 2.1 Output: The printf() method In Listing 1 we used a method called printf() to display a string of characters to the command prompt. We don t just have to print static text however, we can also get it to display values computed inside the program. The listing below gives an example of this and an example of how to assign a Integer type variable value in C. Go to find and read description of printf() function (or least have a look at examples). Listing 2: Ex2.cpp int number = 120; printf ( number ); return 0; Completion 1 Predict what will happen if you try to compile, build and run this code. Try it. Does your prediction match? Correct the code. Include corrected code in 3

4 your report. If you re confused, see below The printf() command expects a String type variable, whereas in Listing 2 we give it an integer type instead. The printf( %d, number); command fixes this by telling the printf() function what variable type we are passing it ( %d indicates an integer(d for decimal) type). 2.2 Variable types and Bytes So why do we bother using these pesky different data types? (Some languages, like Python, guess the types for you - which can be handy but can cause problems down the line as well!). In part it s to be clear about how much memory our program will use. There s a handy method called sizeof() that tells us how much memory is allocated for each type of variable in bytes. Core 8 By modifying the code from Listing 2 and the sizeof() method, try and construct a program that prints out the number of bytes used for an integer (int), a character (char), unsigned char (always positive), a double and a long. Tabulate your results in your report. Note that you can declare a variable type without assigning it a value by replacing int number = 120; with int number;. Ignore compliler warnings (not errors ). Core 9 What is size (in bytes) of unsigned char type? What is maximum value of the variable of unsigned char type? The number of bytes of memory assigned to a variable places upper and lower limits on the value it can contain. For example the maximum decimal number that can be stored in 4 bits is signified by binary: 1111 and is equivalent to decimal 15. In this case we would say that 4 bit unsigned binary can store the values 0 through to 15 (so it can store 16 different values). Listing 3: Ex3.cpp unsigned char number = 255; printf ("%d", number ); number = number + 1; printf ("%d", number ); return 0; 4

5 Challenge 1 Type in, compile, build and run code in Listing 3. Explain what is happening. 3 Negative binary numbers However note that all our values so far are positive. What happens if we want to store negative numbers? Listing 4: Ex4.cpp int main () { char a = 127; // can be negative printf ("a=%d\n",a); a = a + 1; printf ("a=%d\n",a); Completion 2 Run code from Listing 4. Explain result. 4 Bit operations in C For this section we will use two numbers, A and B, with the values 60 and 13 respectively. Core 10 State the 8 bit binary values of both A and B. Core 11 Perform the bit-wise logic operation AND on A and B. Convert the output back to a decimal value. Show your working. Core 12 Perform the bit-wise logic operation OR on A and B. Convert the output back to a decimal value. Show your working. 5

6 Core 13 Perform the bit-wise logic operation XOR on A and B. Convert the output back to a decimal value. Show your working. Completion 3 Write a C program that performs the tasks for Core 11, 12 and 13. Start off with unsigned integers and the bitwise operations (AND, OR, XOR) as shown in the Listing below. Listing 5: Ex4.cpp unsigned int A = 60; unsigned int B = 13; // AND is A & B // OR is A B - this is the pipe symbol // XOR is A ^ B // A << 2 indicates a bitshift of A 2 places to the left // B >> 1 indicates a bitshift of B 1 places to the right // For example printf ("%d", A & B); return 0; NOT(a) operation in C is (a). Challenge 2 Using bitwise operations show that Morgan s rule NOT (a b) = NOT (a)ornot (b) is valid at least for all unsigned chars. 6