SPNU151 User guide

SPNU151W January 1998 – March 2023 66AK2E05 , 66AK2H06 , 66AK2H12 , 66AK2H14 , AM1705 , AM1707 , AM1802 , AM1806 , AM1808 , AM1810 , AM5K2E04 , OMAP-L132 , OMAP-L137 , OMAP-L138 , SM470R1B1M-HT , TMS470R1A288 , TMS470R1A384 , TMS470R1A64 , TMS470R1B1M , TMS470R1B512 , TMS470R1B768

7.2.1 High-Level I/O Functions

The high-level functions are the standard C library of stream I/O routines (printf, scanf, fopen, getchar, and so on). These functions call one or more low-level I/O functions to carry out the high-level I/O request. The high-level I/O routines operate on FILE pointers, also called streams.

Portable applications should use only the high-level I/O functions.

To use the high-level I/O functions:

Include the header file stdio.h for each module that references a function.
Allow for 320 bytes of heap space for each I/O stream used in your program. A stream is a source or destination of data that is associated with a peripheral, such as a terminal or keyboard. Streams are buffered using dynamically allocated memory that is taken from the heap. More heap space may be required to support programs that use additional amounts of dynamically allocated memory (calls to malloc()). To set the heap size, use the --heap_size option when linking; see Table 2-22.

For example, given the following C program in a file named main.c:

#include <stdio.h>
void main()
{
   FILE *fid;
   fid = fopen("myfile","w");
   fprintf(fid,"Hello, world\n");
   fclose(fid);
   printf("Hello again, world\n");
}

Issuing the following compiler command compiles, links, and creates main.out from the run-time-support library:

armcl main.c --run_linker --heap_size=400 --library=rtsv4_A_be_eabi.lib --output_file=main.out

Executing main.out results in

Hello, world

being output to a file and

Hello again, world

being output to your host's stdout window.