IO in SPARC

1
I/O in SPARC
2

• In SPARC, using system call printf and scanf is
  an easy way to perform I/O
• These functions perform conversion and extraction
  automatically.

3
printf

• To use printf function, the following must be
  satisfied
• o0 must be containing the address of a null
  terminated string (c-string). A null terminated
  string is a string ended with 1 byte zero.
• For example
• !in your data section
• myString .asciz hello world!
• . . .
• !in your code
• set myString, o0 ! Get the address
  of the label
• call printf !this should print hello world!
• nop

.ascii string Generates the given sequences of
ASCII characters.   .asciz string Generates
the given sequences of ASCII characters. This
pseudo-op appends a null (zero) byte to each
string.
4

• In C
• Print(..Hello world)
• Print(Integer d, someInteger)
• To print out variables value
• you must have your register o1-o5 containing
  the values to be substituted

5

• In C Printf(its d dollars,amount)
• In SPARC
• !assuming your string declared as follow
• myString .asciz its d dollars
• !In your code
• set myString, o0 ! The address of the string
• mov 20, o1 !substitutes for the first d
• call printf !will print its 20 dollars

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d or i Decimal signed integer. o Octal
integer. x or X Hex integer. U Unsigned
integer. c Character. s C-String, i.e. null
terminated string. f Double e or E
Double. g or G Double. n Number of characters
written by this printf.
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• !assuming your string declared as follow
• myString .asciz its d dollars and d cents
• !In your code
• set myString, o0 ! The address of the string
• mov 20, o1 ! substituted for the first d
• mov 5, o2 ! substituted for the second d
• call printf ! Will print its 20
  dollars and 5 cents

8

• To print a string, the address of the substituted
  string must be in the correspondent register.
• For example
• !assuming your strings are in data section as
  follows
• mystring .asciz Hello s!
• name .asciz Michael
• . . .
• ! and your code should be
• set myString, o0 ! address of the output
• set name, o1 ! Address of the substituted string
  
• call printf ! Will print Hello Michael!
• nop

9
scanf

• scanf is used for reading user input
• scanf requires o0 containing the address of a
  c-string containing the input format
• Subsequence registers (o1-o5) contain the
  address of the memory where the input should be
  stored
• d and i always give you a 32-bit (word-size)
  input, so the address must be aligned by word
  boundary (aligned by 4)

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• d or i Decimal signed integer.
• o Octal integer.
• x or X Hex integer.
• U Unsigned integer.
• c Character.
• s C-String, i.e. null terminated string.
• f Double
• e or E Double.
• g or G Double.
• n Number of characters written by this printf.

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• !assuming your strings are in data section as
  follows
• input .word 0 !aligned by 4
• format .asciz d
• . . .
• ! and your code should be
• set format, o0 ! Address of the format
• set input, o1 ! Address of the location for the
  input
• call scanf ! Reads user input, converts to a
• nop ! number and stores at the memory !
  referenced by input

12

• !assuming your strings are in data section as
  follows
• input .word 0 !aligned by 4
• nl .byte 0 ! A byte to store the input \n
• format .asciz dc
• . . .
• ! and your code should be
• set format, o0 ! Address of the format
• set input, o1 ! Address of the location for the
  input
• set nl , o2 ! location for a character
• call scanf ! Reads user input, converts to a
• nop ! number and stores at the memory !
  referenced by input

13

• !assuming your strings are in data section as
  follows
• format .asciz s
• input .asciz !Allocate
  some space for the input string
• . . .
• ! and your code should be
• set format, o0 ! Address of the format
• set input, o1 ! Address of the location
  for the input
• call scanf ! Reads user input
  up to a blank or ENTER key
• nop