Chapter 10 Data types and structures

10.1 Data types and records

Data types

• BOOLEAN: logical values, true or false
• CHAR: single alphanumerical character
• DATE
• INTEGER
• REAL: number with a decimal point
• STRING: sequence of alphanumerical characters

Records

composite data types - a data type constructed using several of the basic data types available in a particular programming language

TYPE
StudentRecord
  DECLARE name : STRING
  DECLARE age : INTEGER
END TYPE

DECLARE Student : StudentRecord
Student.name <- "Smart Chen"
Student.age <- 16

10.2 Arrays

Array

a data structure containing several elements of the same data type

• Index - a numerical indicator of the position of an item in array
• Lower bound - index of first element
• Upper bound - index of last element

DECLARE numList : ARRAY[0:8] OF INTEGER
numList[3] <- 24
DECLARE sudoku : ARRAY[0:8,0:8] OF INTEGER
sudoku[0,0] <- 3

Linear Search

Pseudocode

x
DECLARE numList : ARRAY[1:8] OF INTEGER
DECLARE search : INTEGER
DECLARE i : INTEGER
DECLARE found : BOOLEAN
found <- FALSE
INPUT search
FOR i <- 1 to length
 IF
   numList[i] = search
   THEN
     OUTPUT “Found at:”, i
     found <- TRUE
 ENDIF
NEXT i
IF
 found = FALSE
 THEN
   OUTPUT “Not found”
ENDIF

Python

l = [6, 3, 0, 5, 1, 2, 8, -1, 4]
search = int(input())
for i in range(len(l)):
    if l[i] == search:
        index = i
        print(f"Found at: {index}")
        break
else:
    index = -1
    print("Not found")

Bubble Sort

Pseudocode

x
DECLARE a : ARRAY[1:8] OF INTEGER
DECLARE swap : BOOLEAN
DECLARE i : INTEGER
DECLARE j : INTEGER
DECLARE temp : INTEGER
i <- 1
swap <- TRUE
WHILE i <= LENGTH(a)-1 AND swap:
  swap = FALSE
  FOR j <- 1 to LENGTH(a)-i-1: 
    IF
      a[j] > a[j+1]
      THEN
        temp <- a[j]
        a[j] <- a[j+1]
        a[j+1] <- temp
        swap <- TRUE
    ENDIF
ENDWHILE

Python

xxxxxxxxxx
a = [5, 3, 7, 2, 1, 8, 4, 6]
for i in range(len(a)-1):
    finished = 1
    for j in range(len(a)-i-1):
        if a[j] > a[j+1]:
            a[j], a[j+1] = a[j+1], a[j]
            finished = 0
    if finished: break

10.3 Files

3 modes of open files

• READ
• WRITE: writes data to the file, any existing data stored in the file will be overwritten
• APPEND: adds data to the end of the file

xxxxxxxxxx
DECLARE firstLine : STRING

OPEN file.txt FOR READ
READFILE file.txt, firstLine
CLOSEFILE file.txt

OPEN file.txt FOR APPEND
WRITEFILE file.txt, "this is the second line"
CLOSEFILE file.txt

10.4 Abstract data types (ADT)

ADT: a collection of data and a set of operations on that data

Stack

a list containing several items operating on the last in, first out (LIFO) principle

• push
• pop

Queue

a list containing several items operating on the first in, first out (FIFO) principle.

• enqueue
• dequeue

Linked list

a list containing several items in which each item in the list points to the next item in the list.

• append
• insert
• delete