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Lecture 13

Midterm overview

When you know a thing, to hold that you know it, and when you do not know a thing, to allow that you do not

know it: this is knowledge

Conficus, Analects

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Problem 1 (10 points)Describe in one sentence the difference between each of the following:

1)write and writelnwrite prints enclosed expression and leaves the cursor on the same

line, while writeln places cursor to the beginning of the next line (via CL/CR).

2)integer and realAn integer variables in Pascal represent whole numbers from

mathematics with system dependent bounded range, while real variables in Pascal represent decimal numbers from mathematics with system depended bounded range.

3)chr and ord

chr function returns a character given an ASCII code, while ord function returns an ASCII code of a given character.

4)writeln( ‘Hello’ ) and writeln( ‘’’Hello’’’ )First one prints Hello, second prints ‘Hello’.

e) Mr. Pascal and Mr. WirthPascal was a French mathematician after whom Wirth named the

language we are studding

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Problem 2 (10 points)What is the purpose of each of the following menu items in TP

a)RunExecutes the program

b) CompileChecks the program for errors and converts to

machine codes

3)Step overExecute current line of code

4)Add watchStart observing a variable

5)Add breakpointMark a line on which the execution of program

should pause.

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Problem 4 (5 points)

Find as many mistakes as you can in the following program

Progrm My Big MistakeBegin;

Readln( iMyInt );iAnswer := iAnswer / iMyInt;writeline( ‘Answer is ‘, ‘iAnswer’ );

enD

Mistakes:

1) Progrm should be spelled Program

2) No spaces in the program name are allowed

3) Missing semicolon after program name

4) Shouldn't have semicolon after begin

5) Need to declare variables

6) writeline should be spelled writeln

7) in the writeln, the iAnswer variable shouldn't be enclosed in quotes

8) There should be a period after enD

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Problem 5 part a)

What would be printed by each of the following programs?

PROGRAM TRICKY1;VAR one, two, count : integer;BEGINone := 10;two := 0;for count := 1 to 2 doBEGIN two := two + one; for one := 1 to 2 do;ENDwriteln( two );END

Result(s)

12

One Two Count

init 10 0

for count := 1 to 2 do (I) 1

two := two + one 10

for one := 1 to 2 do (I)1

for one := 1 to 2 do (II) 2

for count := 1 to 2 do (II) 2

two := two + one 12

for one := 1 to 2 do (I)1

for one := 1 to 2 do (II) 2

writeln(two) produces 12

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Problem 5 part b)

PROGRAM Tricky2;VAR count1, count2 : integer;BEGIN FOR count1 := 1 TO 10 DO FOR count2 := 1 TO count1 DO BEGIN writeln( count1 ); count1 := count2 * 10; END;END.

Result(s)

1

count1 count2

for count1 := 1 TO 10 do (I) 1for count2 := 1 TO count1 do (I)

1(note really count2 :=1 to 1)writeln( count1 ); produces 1count1 := count2 * 10; 10(inner loop exits)count1 is 10 so outer loop exits as well

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Problem 6 (5 points)

How many times will each of the following loops be executed?

Loop Number of times

a) FOR I:=1 TO 101 DO 101

b) FOR I:= ‘a’ TO ‘c’ DO 3

c) FOR I:= ‘a’ TO ‘z’ DO 26

d) FOR I:= 1 DOWNTO 100 DO 0

e) FOR I:= ‘z’ DOWNTO ‘z’ DO 1

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Problem 7 (10 Points)

Factorial of a number N (written as N!) is defined as a product of all numbers starting from 1 up to N. That is, N! = 1*2*3*…*(N-2)*(N-1)*N.

Write a Pascal program, which reads in a positive integer and outputs the value of N!

Program Factorial;var iNumber, iFactorial, iLoopCount : integer;begin

writeln( ‘Please enter a positive integer: ‘ );readln( iNumber );

iFactorial := 1;for iLoopCount := 1 to iNumber dobegin

iFactorial := iFactorial * iLoopCount;end;writeln( iNumber,’! = ‘, iFactorial );

end.

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Problem 8 (10 points)

Write a Pascal program which reads in two positive integers a and b and then determines the remainder and the whole part when a is divided by b.

The program should output a = b*c + d, where c is the whole part and d is the remainder.

Program AgainDivAndMod;var a, b, c, d : integer;begin

writeln( ‘Enter a, b );readln( a, b );c := a div b;d := a mod b;writeln( a, ‘ = ‘, b, ‘*’, c, ‘+’, d );

end.

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Problem 9 (15 points)

Write a Pascal program (utilizing for-loop), that prints every letter of the alphabet and its ‘opposite’. That is, the first few output lines should look like this:‘a’ – ‘z’‘b’ – ‘y’‘c’ – ‘x’etc.

PROGRAM OppositeLetter;

VAR c1 : char;

BEGIN

FOR c1 := 'a' TO 'z' DO

BEGIN

writeln( c1, ' - ', chr( ord( 'z' ) - ord( c1 ) + ord ( 'a' ) ) );

END;

END.

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Problem 10 (15 points)Write a Pascal program, which prints out formatted multiplication table.The table’s rows and columns should run from 1 to 9. Make sure that your

table is formatted well. Use loops to do this problem.PROGRAM MultiplicationTable;

VAR iLoopCount1, iLoopCount2 : integer;

BEGIN

{ Column headings }

write( ' ' );

for iLoopCount1 :=1 to 9 do

begin

write( iLoopCount1:4 );

end;

writeln;

for iLoopCount1 := 1 to 9 do

begin

{ Row heading }

write( iLoopCount1 );

for iLoopCount2 := 1 to 9 do

begin

{ The value at iLoopCount1 column and iLoopCount2 row }

write( (iLoopCount1*iLoopCount2):4 );

end;

writeln;

end;

end.

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Home work

• Start reading chapter 6 ( Sections 1,2 )