Pay particular attention to the section on stack frames for functions Read the sections on "Register Usage" and These conventions form part of the Applicationīinary Interface (ABI). The registers and stack are used by the C compiler, and make your assemblyĬode consistent with it. Since your assembly function will be called from C, and you will beĬalling functions that are written in C, you will have to determine how PrintDec with the appropriate parameter, as shown in theĭiagram below: More on the Nios II Application Binary Interface Will need to call a proper print function from one In summary, the main program will be responsible for calling That the number of integers matches the size of the string specifiedįor example, let's use printn to print the number 10 in YouĬan assume that the printn function will always be called so The second and subsequent parameters are the integers you want to print. the format in which the numbers will be printed: 'O'.The size of the string (in C, the end of a string is indicated by how many numbers are to be printed as determined by.Specifies a string (pointer to null-terminated array of chars) that defines two things:
Number of integers, printing each integer in one of three number formats The printn function's purpose is to print out a variable "." in C means a variable number of arguments, similar to printf or scanf. The printn function takes one string parameter ( fmt)įollowed by zero or more integer parameters. Use the three C functions from Part 1 to do the printing by calling them from yourįunction, in C syntax, looks as follows: void printn ( char *fmt. Which should print out each number in either octal, hexadecimal, or decimal.
The main function calls a function called The program begins executing in the C main function. In this part, you are to write an assembly function that is both called by a C function,Īnd calls other C functions. Part 2: Being called by a function (2 marks) Hint: The assembly program should need around 10 instructions.There will be some startup code from the C library that executes before main is called.Make a global label main as the entry point to your program, since theĬ runtime expects your program to always begin at main. Add lab3_print.c and yourĪssembly code (lab3_part1_main.s) to your project. Since your project will include C files, set the project type to "C Program".Write an assembly program that prints out 10 in octal, hexadecimal, and decimal. Preparation: Do the questions from the Preparation section below before attempting to write the code. Integer parameter and prints it out (on the Monitor program's Terminal) as an octal, hexadecimal, and decimal number, respectively: void printOct ( int val ) įor example, calling printOct(10) results in 12 being printed on the terminal. In this lab, you are provided with three functions in C (that obey the Nios II ABI). Without needing to know the internal details of the functions. Following an ABI allows functions to call other functions This set of rules is commonly knownĪs an Application Binary Interface (ABI).
#HOW TO WRITE C CODE FUNCTIONS HOW TO#
How to pass parameters from caller to callee, how to pass a return value back to the caller,Īnd what registers a function is allowed to modify ("clobber"). People (or compilers), functions must agree on a common set of rules on how they interact: Since functions are often written by different Modules that can be easily composed together. The purpose of a subroutine is to decompose a larger program into relatively self-contained Writing assembly language subroutines that call and are called by C subroutines. The purpose of this lab is to introduce subroutines, by
More on the Nios II Application Binary Interface Lab 3: Subroutines and C Lab 3: Subroutines and C
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