More SIMPLESEM Examples

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More SIMPLESEM Examples

• CSCI 169 - Oleg Aulov
• A. Bellaachia

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Review

• Semantics
• SIMPLESEM
• C1 - simple statements only

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C2 and C2 - simple routines

• Global data
• Routine declarations and definitions
• Main() routine
• C2 - separate compilation

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C2 - program example
int i1,j2,k3 alpha() int i4,l5
ikl
beta() int k6 ijk alpha()

main() beta()
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C3 - recursive functions

• Direct recursion
• Indirect recursion

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C3 - implimentation needs

• Base address (known at exec time only)
• LIFO stack
• Return pointer
• Dynamic link / dynamic chain

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C3 - program example
int n int fact() int loc if(ngt1)
locn-- return loc fact() else
return 1
main() get(n) if(ngt0)
print(fact()) else print(input
error)
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• Show Examples on a SIMPLESEM

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Example of C2
0 set 0,read 1 set 1,read 2 set 2,read 3 set
6,5 4 jump 10 5 halt 6 set 4,4 7 set 5,5
8 set 4, D4D2D5 9 jump D3 10 set 7,6 11
set 0, D1D7 12 set 3, 14 13 jump 6 14 jump
D6
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Example of C3
14 set D0 2, D2 15 set 2, D2 - 1 16 set
1, D1 1 17 set D1, ip 4 18 set D1 1,
D0 19 set 0, D1 20 set 1, D1 3 21 jump
13 22 set D0 - 1, DD0 2 DD1 - 1 23
jump 25 24 set D0 - 1, 1 25 set 1, D0 26 set
0, DD0 1 27 jump DD1
0 set 1,3 1 set 2, read 2 jumpt 11, D2 lt 0 3
set 1, D1 1 4 set D1, ip 4 5 set D1
1, D0 6 set 0, D1 7 set 1, D1 3 8 jump
13 9 set write, DD1 - 1 10 jump 12 11 set
write, "input error" 12 halt 13 jumpt 24, D2
lt 1