INFO 1006 Computer Architecture –practice paper 2
main tasks:
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Number System Exercises
Printing in binary or decimal
Specifying numbers in hex
Number & character representation in the SIM20
Getting keyboard input
Use of the insert command
Level 1: Basic Course
Requirement
Number System Exercises
1.1 Convert these decimal numbers into their required forms
Octal
Binary
Hexadecimal
22
751
1453
Tips: In compare to the decimal system which has column headings that go up
multiplying by ten each time (1, 10, 100, 1000 and so on)
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1.2
1.3
Marks
4.5
Binary system has column headings that go up multiplying by two each
time (1, 2, 4, 8, 16 and so on). See the figure of "counting up in
Binary" at the end of the paper for more detail.
Octal system has column headings that go up multiplying by eight each
time (1, 8, 64, and so on…). See the figure of "counting up in Octal "
at the end of the paper for more detail.
Hexadecimal system has column headings that go up multiplying by
sixteen each time (1, 16, 256, and so on…). In order to store the digits
from 0 to 15, six alphabets were introduced to cover the range from ten
to fifteen: A (=10), B (=11), C (=12), D (=13), E (=14), F (=15). See
the figure of "counting up in Hexadecimal" at the end of the paper for
more detail.
Convert these octal numbers into their required forms
Decimal
Binary
Hexadecimal
73
3733
Convert these hexadecimal numbers into their required forms
3
1.5
Decimal
6A
EF
6DA
Designed by Lisha (Feb-08)
- Part of the information was picked from the course notes
Page 1
1.4
1.5
Convert this binary number into their required forms
Octal
Hexadecimal
11011101010110101011
1111000001
Find the two's complement of the following binary numbers, and then add the
binary number 01010000 to each of the two's complement numbers that you
worked out
2
2
Binary numbers
The two's complement
+ 01010000
00110101
01000000
Tips: you should have 00011011 and 00010000 as your answers. Check your
results by converting all the numbers from binary to decimal and working it
out again in decimal.
1.6
Work out the following additions for three bit binary numbers in two's
complement. In each case, determine whether or not overflow has occurred:
Result
1.7
2
Overflow (Yes / No)
10011100 + 00100011
11001010 + 10001000
Convert the following numbers into floating point format:
37900194000
0.234
2344
0.0000128394
Printing in binary or decimal
1.8
Get ready: Compile and run the example program when CECIL is loaded
2
Marks
3
Printing in binary:
 Change the program title, (for example: printing in binary), the author,
and the date, add your comments
 Change "print" to "printb" to print the answer in binary
 Compile and run your program
 You should have an answer of "0000010111" which is "23" in binary.
 Save your program
1.9
Printing in hexadecimal:
 Change the program title, (for example: printing in hexadecimal), the
author, and the date, add your comments
 Add a $ in front of 12 (the value of data1) and 11 (the value of data2)
 Compile and run your program
 You should have an answer of "0000100011" which is "35" in binary.
 Save your program
Designed by Lisha (Feb-08)
- Part of the information was picked from the course notes
4
Page 2
Number & character representation in the SIM20
1.10 Run CECIL, enter header and comments to your preference.
 Enter code:
.start
load
print
printb
printch
stop
;
;--- now the data follows--;
.data
insert
;
;---end of source code--
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Up to 10 marks
4
data
65
compile and run your program
observe the output
o hints: you should have “650001000001A” as your answer, this
is because print prints numerical values, printb prints in binary,
printch prints in ASCII format.
1.11 Load and printch “cr” and “lf”, in the data section insert value 13 for “cr” and
10 for “lf” every time before you print the value out in another format
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observe the output
o hints: you should have the output of 65, 0001000001, and A in
three separated lines. This is because CR moves to the start of
the line and LF moves vertically down a line, so, using two of
them together, you can achieve a new line.
Save your program
You are encouraged to have free experiments with other ASCII codes
that control the screen layout.
Getting keyboard input
1.12 Use “getkey” to get a character from the keyboard
 Enter “getkey”, -- place it after the “.start”
.start
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4
Marks
4
getkey
Print the keyboard input in three different ways - numerical values,
binary, and ASCII format.
printch
printb
print
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Compile and run your program.
o Hints: this code will take a keyboard input character and display
the out put of three formats all together in one line
Designed by Lisha (Feb-08)
- Part of the information was picked from the course notes
Page 3
Use of the insert command in CECIL
1.13
 Enter header, comments and the code below:
.start
load mesg1
printch
load mesg2
printch
stop
;
;--- now the data follows--;
.mesg1
insert "H"
.mesg2
insert "I"
;
;---end of source code---
Marks
4
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Compile and run the program
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You should have a message of "HI" as your out put, explain it briefly.
o hints: CECIL provides a way of giving it the letter, and
it converts it to ASCII, so that you don't need to
remember the ASCII codes or look them up all the time.
Total marks: 40
Level 2:
Further Development
Number & character representation in the SIM20
Up to 5 marks
2.1 Write yourself a program that loads a number into the A-register and then prints 10
it out in the three different ways.
Getting keyboard input
Up to 5 marks
2.2 Write a program that gets a number keypress from the keyboard and then display 10
it as that number
Use of the insert command in CECIL
Up to 5 marks
2.3 Write a program to print a short message out on the SIM20 screen.
10
Total marks: 30
Designed by Lisha (Feb-08)
- Part of the information was picked from the course notes
Page 4
Level 3: Challenge for experienced
students
Number System Exercises
Marks
3.1 Magic Square: Using the nine hexadecimal numbers from A to 12, fill in the 10
following magic square so that each row, column and diagonal adds up to the
same amount.
hints: Each row, column and diagonal should add up to 2A; Try and work out
which number should go in the centre square
3.2
Subsets: A set of things - e.g. the days of the week, {Monday, Tuesday, 10
Wednesday, Thursday, Friday, Saturday, Sunday} - can have a number of
subsets - e.g. the weekend, {Saturday, Sunday}. Work out a formula for the
number of subsets that a particular set can have.
hints: Think in terms of binary numbers
Printing in binary or decimal
Marks
3.3 Write a program to print a short message out on the SIM20 screen, and take a 10
key board input character as an answer, and prints it out in three different
formats, each of them display in a new line.
Total marks: 30
Here are the programs, tables that mentioned in this practice paper, you can also find them
from the course web site.
Column Heading 128 64
1
1
1
1
1
1
32
1
1
1
16
8
4
1
1
------ etc ----1
1
1
1
1
1
1
1
1
2
1
1
0
0
1
0
1
0
1
0
1
Value
0
1
2
3
4
5
0
1
1
1
0
1
253
254
255
Figure 1: Counting up in Binary
Designed by Lisha (Feb-08)
- Part of the information was picked from the course notes
Page 5
Column Heading
16
1
Value
0
0
0
0
1
1
0
2
2
------ etc --------0
A
10
0
B
11
0
C
12
0
D
13
0
E
14
0
F
15
1
0
16
Figure 2: Counting up in Hexadecimal
Column Heading
64
0
0
0
0
0
1
3
8
1
Value
0
0
0
0
1
1
------ etc --------1
0
8
1
1
9
------ etc --------7
7
63
0
0
64
------ etc --------7
7
255
Figure 3: Counting up in Octal
Designed by Lisha (Feb-08)
- Part of the information was picked from the course notes
Page 6