Programming Languages Exam

Name ______________________________

This is a long exam. Do not get bogged down on any question. Do the ones you can do first.

The total number of points you can earn on this exam is 105.

If you estimate your total earned points within 5 points of your actual earned points, I will add 5 points to your total score. You do not have to add up your points, it is sufficient to indicate the points per page in the empty column.

Question Page	Max Points Possible	Estimated Earned Points	Actual Earned Points
Short Answers – page 1	10
Short Answers – page 2	12
Short Answers – page 3	8
Scope Question	10
FOR LOOP	10
Grammar Question	15
Comparative Languages	15
Parameter Passing	16
Ada For Loop Question	10
	105

I have observed the provisions of the honor code in completing this exam.

_______________________

Signature

Programming Languages Exam

Short Answers - Page 1

Name ____________ Max Points: 10 Points Earned: _____

Our text book lists five (5) reasons for studying the concepts of programming languages. Briefly but clearly describe three (3) of them.

1. increased capacity to express ideas

2. improved background for choosing appropriate languages

3. increased ability to learn new languages

4. better understanding of the significance of implementation

5. overall advancement of computing

Our book lists the three most important criteria for evaluating a programming language as readabilit, writability and reliability. Pick one of these and list three (3) programming language elements that affect it.

Criterion:

readability

writability

reliability

Element 1

simplicity/orthogonality

control structures

simplicity/orthogonality

control structures

simplicity/orthogonality

control structures

Element 2

data types & structures

syntax design

data types & Structures

syntax design

data types & Structures

Element 3

syntax design

support for abstraction

expressivity

support for abstraction

expressivity

type checking

exception handling

restricted aliasing

Our book indicates discusses the six (6) programming "domains" below. For 4 of them, indicate a language that is representative of the domain

Domain	Representative Language
scientific applications	FORTRAN or Algol 60
business applications	COBOL
artificial intelligence	LISP or Scheme or Prolog
systems programming	C or PL/S or BLISS or extended Algol
scripting languages	JavaScript or Perl or PHP
special purpose languages	rpg or apt or gpss

Programming Languages Exam

Short Answers - Page 2

Name ____________ Max Points: 12 Points Earned: _____

Our book says that a variable is a sextuple of attributes. Identify three (3) of these attributes and describe what is meant when we refer to them.

Attribute	Description
1. name	how the programmer refers to it
2. address	memory location (address) with which it is associated
3. value	contents of abstract memory cell
4. type	its set of values and its set of operations
5. lifetime	when is it accessible
6. scope	where is the variable known

We have discussed two types of bindings: static and dynamic. Provide a definition for static binding and tell where we might see an example of a statically bound variable in a programming language.

Definition:

first occurs before run time and remains unchanged throughout program execution

Example:

assignment of value to a constant; association of main program variables with memory locations

What is the difference in the use of indentation in FORTRAN and in Pascal?

in FORTRAN: indentation is meaningful. Statements and labels are required to be in specific columns

in Pascal: indentation is only an aid to the understanding of the person reading the code

What is the difference between discrete types and scalar types?

discrete types are: those such that between any two successive values, there is no other value types which are mathematically discrete

scalar types are: types which do not have component parts

include floating point which is not discrete because between any two floating point numbers there are other numbers

Programming Languages Exam

Short Answers - Page 3

Name ____________ Max Points: 8 Points Earned: _____

FORTRAN uses implicit type declarations while Ada and Pascal do not.

What do we mean by implicit typing?

when the value or name assigned to a variable determines its type

Do you consider implicit typing a plus or a minus?

a plus -

a minus -

Why?

plus makes the language more flexible

minus makes the language less safe - doesn't catch certain kinds of programmer errors

Pascal programs are single compilation units while Ada and FORTRAN programs can consist of multiple compilation units.

Which do you think is a better approach?

single

multiple

Why? (i.e. what is an advantage of the approach you think is better)

single means everything is bundled together and you can see it all at once

multiple makes it possible to separately compile (and test) each unit

Some programming languages have key words, and some languages have reserved words.

What is a reserved word?

A reserved word is a word that may not be used as a variable or program unit name in a program

Give an example of a reserved word in a language we've looked at this semester:

procedure

What language did your reserved word come from?

Ada

Note: integer and writeln aren't reserved words in Pascal

FORTRAN doesn't have reserved words

Programming Languages Exam

Scope Question

Name ____________ Max Points: 10 Points Earned: _____

Here's a program written in pseudocode (although it may look like a real language).

program a;

const x = 4;

var z: integer;

procedure p(x: integer);

var y : integer;

begin {p}

y := z +x;

print (y);

end procedure p;

procedure q (x : integer);

var z: integer;

procedure r:

var y : integer;

begin {r}

y := z * 8;

p(y);

end procedure r;

begin {q}

z := 9;

end procedure q;

begin {a}

z := 7;

q(x);

end program a;

What value will be printed if we assume that the program is using static scope rules? 79

What value will be printed if we assume that the program is using dynamic scope rules? 81

Programming Languages Exam

FOR LOOP

Name ____________ Max Points: 10 Points Earned: _____

Here is a pseudo-code for loop (which represents a syntactically correct Pascal, Ada or Java FOR loop or a FORTRAN DO loop. Answer each of the questions which follow the loop with regard to any three of the following four languages: FORTRAN, Pascal, Ada and Java. Cross out the column for the language you are not choosing.

var m, n : integer;

for i := m to n do

begin

output i

<3>

end;

Question	FORTRAN	Pascal	Ada	Java
Can the programmer assign a value to i at point <3>?	yes/no*	yes	no	yes
Is it possible to jump out of the loop at point <3>	yes	yes	yes	yes
Does i have to be explicitly declared anywhere?	no	yes	no	yes
Is it possible to increment i by a value other than 1?	yes	no	no	yes

* the compiler most of you were using didn't allow it. FORTRAN IV did

Programming Languages Exam

Grammar Question

Name ____________ Max Points: 15 Points Earned: _____

Given the language specification below

<someAs> ::= a a

<someBs> ::= b

a. Draw 5 different parse trees generating legal strings in this language

<start>

/ \

/ | \ |

a a <someAs> b

/ \

a a

<start>

/ \

/ \ |

a a b

<start>

/ \

/ \ / | \

a a b b <someBs>

<start>

/ \

/ | \ / | \

a a <someAs> b b <someBs>

/ \ |

a a b

<start>

/ \

/ | \ / | \

a a <someAs> b b <someBs>

/ \ / | \

a a b b <someBs>

b. Show each of the strings you generated

a a a a b a a b a a b b b a a a a b b b a a a a b b b b b

c. Describe in concise English what the strings in this language consist of. Be careful to be accurate and precise.

An even number of As followed by an odd number of Bs. There must be at least 2 As and 1 B.

Programming Languages Exam

Comparative Languages

Name ____________ Max Points: 15 Points Earned: _____

Rewrite the FORTRAN code containing computed GOTO statement shown below in Ada without GOTO statements. Only write what is necessary to replace this statement. Assume that all declarations, etc. are in place.

with ada.text_io;
with Ada.integer_text_io;
number : integer;
if (number = 1) then
     number := number + 73;
else
     if (number = 2) then
     number := number * 7;
      else
     if (number = 3) then
          number := 23;
       end if;
    end if;
end if;
   number := number * number * number;

GOTO (30,40,50) NUMBER

30 NUMBER = NUMBER + 3

GOTO 60

40 NUMBER = NUMBER * 7

GOTO 60

50 NUMBER = 23

60 NUMBER = NUMBER * NUMBER * NUMBER

What would be stored in the memory locations shown below after execution of the following FORTRAN input statement? The input data is shown in the box below.

READ (5, 20) A,B, I, X

20 FORMAT (F2.1, F3.2, I4, F4.1)

3254657384729385712

A	3.2
B	5.46
I	5738
X	479.2

Write the FORTRAN output and FORMAT statements that would output each of the stored values with a single space separating each from the other.

WRITE (6, 21) A,B,I,X

21 FORMAT (1X, F3.1, 1X, F4.2, 1X, I4, 1X, F5.1)

Show the output produced by the output statement you wrote above. (Each box represents an output column)

Programming Languages Exam

Parameter Passing

Name ____________ Max Points: 16 Points Earned: _____

Below is a pseudo-code subprogram.

subprogram swap ( aReal3, aReal2)

local variable x

x <- aReal 3

aReal3 <- aReal2

aReal2 <- x

end subprogram swap

Each part of this question asks you what will be printed upon return from the subprogram assuming that the pseudo-code represents syntactically correct code in the language specified. For each part, you should assume that:

value1 and value2 are variables holding a legal real (i.e. floating point) value

value1 is initially holding 23.45

value2 is initially -92.13

swap is called with parameters value1, value2 in that order

In each case, what will be printed after the return from swap, if value1 is printed followed by value2?

a. The language is FORTRAN

Value1	-92.13
Value2	23.45

b. The language is Pascal and aReal3 is a var parameter and aReal2 is a value parameter

Value1	-92.13
Value2	-92.13

c. The language is Ada and both parameters are in out parameters

Value1	-92.13
Value2	23.45

d. The language is Java

Value1	23.45
Value2	-92.13

Programming Languages Exam

Ada For Loop Question

Name ____________ Max Points: 10 Points Earned: _____

with Ada.Integer_text_io;
with Ada.text_io;

procedure testLoopFor is

i : integer := 7;

begin
for i in reverse 4..6 loop
    ada.Integer_text_io.put (i,3);
    for i in 3..5 loop
      ada.Integer_text_io.put (i,3);
    end loop;
    ada.Integer_text_io.put (i,3);
end loop;
ada.Integer_text_io.put (i,3);
end testLoopFor;_

The questions below all refer to the Ada code above

a. Will the above Ada program compile? It won't but I intended it to! Inadvertent understcore (in red above) is the problem. It was a typo

¼§Ïtestloopforb.adb:17:18: identifier cannot start with underline

b. Show the output!

Ï«Ï ----jGRASP exec: C:\GNAT\bin\testLoopForB
ÏÏ§Ï
ÏÏ§Ï 6 3 4 5 6 5 3 4 5 5 4 3 4 5 4 7
ÏÏ§Ï
ÏÏ©Ï ----jGRASP: operation complete.

c. How many numbers will be printed? 16

d. How many times will the number 6 be printed? 2

e. How many times will the number 3 be printed? 3