221-programming-techniques

Question 1

Computer program

Answer 1

series of statements (instructions) that are executed (run) one after the other
- accept input, process data, produce output

Question 2

Programming constructs

Answer 2

controls the flow of the program
iteration sequence, selection

Question 3

sequence

Answer 3

the order of which code statements are executed
from top to bottom until the end of the program is reached/another construct
- important as carrying out instructions in wrong order lead to incorrect performing

Question 4

selection

Answer 4

changes program flow based on outcome og logical decision e.g if statements
allows program to branch as
section of code is only run if condition is met

Question 5

iteration

Answer 5

loops used to repeat sections of code for execution

count controlled e.g for loop - for a certain amount of time, required iterations is known ahead of time

condition controlled e.g while loop - until condition is met, when number of iterations is not known

• simplifies program, fewer lines of code, less error prone
• more flexible, can just change loop value to change number of iterations

Question 6

nesting

Answer 6

putting one statement inside of another, achieved by either iteration or selection/both

Question 7

recursion

Answer 7

• a function that calls itself within itself
• for any input value other than stopping condition, it should call itself
• the stopping condition should be finitely reachable or else stack overflow (indefinite calls)
• each call creates a stack frame (new instance of a function with its own copy of local variables and parameters and return address - code point)
• frames placed on the stack
• then stopping, they pop off until stack emptied, return results are cascaded down to caller until initial caller

Question 8

recursion pros and cons

Answer 8

• more quick to read, easier to represent/ less lines of code as some functions/problems are naturally recursive
• suited to certain problems e.g tree traversal and some sorts
• can reduce the size of the problem each call e.g divide and conquer
• deep -> runs out of stack space if too many calls and crash occurs (overflow)
• more difficult to trace flow and debug, each function on the stack has its own set of variables
• less intuitive for those unfamilar
• inefficient use of memory
• can be slower as overhead stack maintenance

Question 9

call stack

Answer 9

stores the local variables, parameters, and the return address when a function is called
when functions complete execution, they are popped off

Question 10

iteration pros and cons

Answer 10

• more memory efficient, requires less
• no stack overflow
• easier to understand, debug read, and trace as straightforward
• recursive declares new variables/stack push, iterative uses the same variables
• for problems that can be naturally expressed iteratively
• more lines of code, potentially harder to understand when implemented to recursive problems (representation)

Question 11

tail recursion

Answer 11

• keeps an accumulated total of the value we are calculating
• usually using a accumulator parameter
• reduces computation, no additional calculations after recursive call returns as final recursive return value is the final return value

Question 12

variable

Answer 12

labelled memory location (identifier) that stores value that can be changed during running time

Question 13

constant

Answer 13

labelled memory location whose value remains fixed
does not change during program running
must be set when written

Question 14

assignment

Answer 14

supplies a value to constant or variable, performed with a = symbol

Question 15

scope

Answer 15

global or local
refers to the section of code for which variable is available in when declared

Question 16

global variable

Answer 16

-can accessed/changed throughout entire program. useful for values need to be used by multiple parts
- declared global/ in main body at top, simple.
- good practice to avoid global variables e.g if 2 functions try to access global variable at same time, conflicts and cluttered namespace
- harder to test, debug, maintain, returning values much safer
-created when program starts, destroyed when end, more memory alloc

Question 17

local variable

Answer 17

declared within function/procedure
can only be accessed within that block
- memory efficient, released from memory
- reusability: multiple same names can exist in different subroutines, unaffected
- self contained and encapsulated, no unintended outside changes
-if local variable has same name as global, local precedence
- code redundancy, same purpose/value across subs

Question 18

modularity

Answer 18

functions and procedures
- goal each module carries out specific individual task
- split large complex programs into sub self contained smaller (breaks down and structures)

Question 19

subroutines

Answer 19

section of code that performs a specific task, can be called whenever needed
given a unique name identifier
- problem shorter n easier to understand solve read debug, simplifies testing isolation, parallel team division time save, individually, reusability and existing libraries, avoid repetition, abstraction

Question 19

procedure vs function

Answer 19

both performs specific task when called
procedure does not return any value, function does
both can have any many parameters. are subroutines

Question 20

parameter vs argument

Answer 20

Parameters are variables initalised in the function’s definition for it to accept inputs. Specifies what function expects. Act as placeholder for the values (arguments) when called
Argument are the values passed into function/procedure filling the parameters
- by reference or value
- reference is address of original value, og value updated if any changes made
- value is copy of og value, treated as a local variable, new space for it and end discarded, og value outside not affected

Question 21

string manipulation

Answer 21

stringname.length

conversion
stringname.upper()
stringname.lower()
ord(”A”) gives ASCII, can use ASC
chr(65) gives char

boolean
stringname.isupper()
stringname.islower()

Question 22

file manipulation pseudocode

Answer 22

file=openWrite(“s.txt”)
file=openRead(“s.txt”)
file.writeLine(“Hello”)
file.close()
x =file.readLine()
while NOT file.endOfFile():
print(myFile.readLine()

Question 23

IDE (integrated developer environment)

Answer 23

software/ program used to write code
provides tools and features to help developer write, test, debug
editors, error diagnostics, run time environment, translator
speed up development and productivity
suitable for beginners, simple
autocompletion/indentation, syntax highlighting, integrated debugger

Question 24

breakpoints

Answer 24

allows developer to define certain points in program to pause execution on condition/line helps pinpoint and identify logic errors

Question 25

stepping

Answer 25

step through/execute code line by one at a time to locate error and monitor effect of each line Variable checks shows the values of the variables currently stored in memory whilst stepping through the code, observe how contents change real time

Question 26

runtime environment

Answer 26

infrastructure supports execution and running of code, enable developer to check for runtime errors and test program without fully compiling it

Question 27

auto documentation

Answer 27

analyse source code tracks declared variables, modules, comments - produces documentation to aid in maintenance, debugging, support

Question 28

syntax highlighting

Answer 28

easier to read/identify syntax errors as coding

Question 29

error diagnostics

Answer 29

diagnostics displays full report on syntax and runtime errors during and location during compilation, sometimes suggests fixes

Question 30

syntax completion

Answer 30

as you type, suggests/correct code quicker to type, less errors

Question 31

code editor

Answer 31

area to write and edit source code often supports additions like autocomplete, autoindent, syntax highlighting

Question 32

operator

Answer 32

character that represents an action e.g +