1. LOGICAL CONTROL STRUCTURES (chp. 8)
1. Sequence – move, add, write, etc.
2. Selection – if
3. Iteration – perform
Function A
Function B
Entry
Exit
true
Function A
Exit
condition
Entry
Function B
false
true
condition
Entry
Exit
Function A
false
Statement Syntax

2. IF STATEMENTS Examples: Syntax Definition: IF condition-1 [THEN]
For Your Information
A condition should evaluate to TRUE or FALSE.
If the condition is true, the statements are executed.
If the condition is false, the ELSE section of statements is executed, if it exists. Remember, the ELSE is optional
Relational operators have equivalent worded clauses. For example, “is less than” and “is greater than or equal to”.
AND and OR go between two conditions that evaluate to true or false.
Conditions are evaluated
Syntax Definition:
IF condition-1 [THEN]
statement(s)-1
[ELSE
statement(s)-2]
[END-IF]
Conditions:
Relational operators: <, >, <=, >=, =
Logical operators: AND, OR, NOT
Reminder:
left right AND OR NOT left
T T T T F
T F F T
F T F T T
F F F F
Examples:
See example code
Statement Syntax

3. CONDITIONS CONDITION-1 can be defined as:
identifier-1 IS [NOT] { identifier-2 }
GREATER THAN (>)
LESS THAN (<)
EQUAL TO (=)
LESS THAN OR EQUAL TO (<=)
GREATER THAN OR EQUAL TO (>=)
{ }
NUMERIC
ALPHABETIC
POSITIVE
NEGATIVE
ZERO
ALPHABETIC-UPPER
ALPHABETIC-LOWER
Statement Syntax

4. MORE ON CONDITIONS COLLATING SEQUENCE – EBCDIC (ibm) and ASCII (unix)
LOW spaces spaces
special characters special characters
a-z 0-9
A-Z A-Z
HIGH a-z
PRECEDENCE
conditions surrounding AND
conditions surrounding OR
AND from left to right
OR from left to right
FYI: use parenthesis to override the above precedence
Examples where a=1, b=2, c=2, d=3
a > c and b > c (true ….. false)
a > c or b > c (true ….. false)
a = b and b = c and a = d (true ….. false)
a = b or b = c or a = d (true ….. false)
a = b or b = c and a = d (true ….. false)
a = b and b = c or a = d (true ….. false)
Examples
“smith” _____ “saunders”
“Smith” _____ “saunders”
“hi” ________ “hello”
“YES” ______ “yes”
“abc123” ______ “123abc”
“aBc” _______ “AbC”
Statement Syntax

5. IMPLIED CONDITIONS OTHER!
The first test in a condition must be a “full test” meaning it evaluates to TRUE or FALSE on its own
The subsequent conditions can have implied operands and/or operators
if a = b and a = c
if a = b and = c
if a = b and c
see example code…
OTHER!
Numeric/alphabetic is a CLASS test
Positive/negative/zero is a SIGN test
should have an S in the pic clause
absolute value example (also in book)
not negative is not equal to positive
not greater than or equal to is equivalent to less than
Statement Syntax

6. CONDITION NAMES Syntax Definition: 88 condition-name VALUE literal
For Your Information
Since a condition should evaluate to true or false, a condition name should also evaluate to true or false.
Like all other level numbers, the condition name level number 88 also appears in the working-storage section of the data division.
Each condition name has an equivalent condition using the 01 level data name. For instance, for example 1:
read input-file
at end move “yes” to eof-switch.
perform para-1 until eof-switch = “yes”
For example 2:
if college-rank = 1 move “FR” to rank-desc
if college-rank = 1 or 2 or 3 or 4
move “UG” to rank-course.
if college-rank > 4 move “G” to rank-course.
Syntax Definition:
88 condition-name VALUE literal
[…] | [THRU | THROUGH literal]
Examples:
01 eof-switch pic xxx value “no”.
88 eof-cond value “yes”.
perform para-1 until eof-cond.
01 college-rank pic 9.
88 rank-fresh value 1.
88 rank-soph value 2.
88 rank-junior value 3.
88 rank-senior value 4.
88 under-grad value
If rank-fresh move “FR” to rank-desc.
If rank-soph move “SO” to rank-desc….
If under-grad move “UG” to rank-course.
If not under-grad move “G” to rank-course.
Statement Syntax

7. EVALUATE STATEMENTS Examples: Syntax Definition: EVALUATE TRUE
{WHEN condition-1 stmt-group-1…}
[WHEN OTHER stmt-group-2]
[END-EVALUATE]
Examples:
Evaluate true
when college-rank = 1
move “FR” to rank-desc
move “UG” to rank-course
when college-rank = 2…
when college-rank = 3…
when college-rank = 4…
when college-rank > 4…
when other perform 500-error-routine
End-evaluate
For Your Information
Equivalent to nested IF structures.
Only the first condition that is true is executed (like an IF structure!).
Can use condition names i.e instead of condition-1 being college-rank = 1, you can use rank-fresh.
Other evaluate syntax definition…
Statement Syntax

8. PERFORM STATEMENTS (chp.9)
For Your Information
“with test before” is the default.
FROM is the initial value of identifier-1
BY is the modifying value for identifier-1
Initialize, test, execute,
modify, test, execute,…
Move 1 to a.
Perform until a > 10
display “a = “ a
add 1 to a
End-perform
Perform varying a from 1 by 1 until a > 10
Q1. What if “”with test after”?
Q2. What is value of “a” once loop has finished executing?!
Q3. What if add/display in different order?
TYPES:
Perform-Until
Perform # Times
Perform Varying
Syntax Definition:
PERFORM [paragraph-name-1]
{identifier-1 | integer-1} TIMES
PERFORM [paragraph-name-1]
[ {THROUGH | THRU} paragraph-name-2 ]
[WITH TEST {BEFORE | AFTER} ]
[VARYING identifier-1
FROM { identifier-2 | integer-2}
BY {identifier-3 | integer-3} ]
UNTIL condition-1
AFTER
Init, exec, test
Mod, exec, test,…
identifier-1| integer-1 must be positive integer or zero
identifier-2 | integer-2 and identifier-3|integer-3 can be positive or negative real values
Statement Syntax