Ordinal types

1
Ordinal types

• An ordinal data type is an ordered set in which
  every element, except the first element, has an
  immediate predecessor, and every element, except
  the last element, has an immediate successor.
• all types of integers
• characters
• boolean
• enumerated types (Enumerated types are user
  defined. We will not cover them in this course)

2
Ordinal types (cont)

• Reals and strings are not ordinal types because
  they do not have a unique predecessor or
  successor.
• A FOR-DO loops control variable must be an
  ordinal type.
• This is why reals cannot be control variables

3
ASCII Table

• ASCII (American Standard Code for Information
  Exchange) table contains 128 entries relating
  whole numbers to characters
• Turbo Pascal extends this table with graphical
  characters. The total number of characters in
  the table for Turbo Pascal is 256 (0 to 255 or
  0000 0000 to 1111 1111).
• A characters position in this table is called
  its ordinal position.

4
Distinction between integer and its character
representation

• The number 6 and the character 6 are not the
  same
• The explicit representation of the character 6 in
  a program is 6 and its ordinal position in the
  ASCII table is 54.
• The explicit representation of the integer 6 in a
  program is 6 and its ordinal position in the
  integer sequence is also 6.

5
Ordinal Functions

• ord(ordinal_type) This function returns the
  ordinal position of the value in the parenthesis.
• ord (A) returns 65
• ord (123) returns 123
• ord (TRUE) returns 1
• ord (FALSE) returns 0

6
Ordinal functions (cont)

• chr(byte)
• give this function an integer between 0 and 255
  and it returns the character whose ordinal value
  is that integer.
• chr(64) returns _at_
• chr(52) returns 4 note this is a character
• chr(87) returns W
• chr(129) returns ü

7
Ordinal functions (cont)

• succ() is the successor function. It returns the
  next value of the ordinal type.
• succ(A) returns B
• succ(3) returns 4
• succ(3) returns 4
• succ(FALSE) returns TRUE
• succ(TRUE) does not have a value

8
Ordinal functions (cont)

• pred() is the predecessor function. It returns
  the previous value of the ordinal type.
• pred(B) returns A
• pred(3) returns 2
• pred(3) returns 2
• pred(FALSE) does not have a value
• pred(TRUE) returns FALSE

9
Converting numbers read as characters to integers

• Sometimes you may want to read numerical digits
  as characters and convert them to numerical
  values in your program. Number ord(char) -
  ord(0)

10
Turbo Pascal Topic Debugging
11
Standard Functions arithmetic

• Sqr(x) squares x
• sqrt(x) positive square root of x
• abs(x) absolute value of x
• exp(x) raises e to x power
• ln(x) log of x to base e
• cos(x) Cosine of x
• sin(x) Sine of x
• arctan(x) Arctangent of x

12
More standard functions

• Transfer functions (real to integer)
• Round(x) rounds x to the closest integer
• trunc (x) drops the part of x to the right of the
  decimal.
• Boolean functions
• odd (x) returns TRUE if x is odd or FALSE if x is
  not
• we will learn others later

13
Turbo Pascal non-standard functions

• Pi the value of pi (note no arguments)
• upcase(L) returns uppercase for a lowercase
  letter L. For any other character it returns the
  same character.
• Frac(x) returns part to the right of the decimal
• int(x) returns part to the left of the decimal
• random(N) returns random integer between 0 and
  N-1
• random returns random real between 0 1

14
Midterm topics

• Variables
• types
• integers
• reals
• boolean
• character
• strings
• rules for naming
• garbage values

15
Midterm topics (cont)

• Arithmetic operators
• integers
• reals
• precedence
• formatting output - all types
• reading data
• buffer
• all types

16
Midterm topics (cont)

• Units
• compiler
• loops
• FOR TO
• FOR DOWNTO
• nested
• ordinal types - all topics

17
Midterm topics (cont)

• Programming
• any topic covered in
• class
• homework
• chapters 1-5
• functions