About program segments

Memory within a computer is typically made of different portions of memory with specialized attributes called segments.

If you have a Fortran or C program, depending on a number of factors, different segments are used to store your variables (data). Following is a list of common variable types and the segments in which they are stored (some of the information below is compiler-specific):

• Fortran code:
  • A regular Fortran 77 array is in the data region when compiling with xlf77 (and variants thereof, for example, mpxlf77).
  • A regular array is in the stack region when compiled with xlf90 (and variants thereof, for example, mpxlf90), unless the array appears in a SAVE statement or a COMMON block, or the -qsave option is used.
  • A Fortran 90 allocatable array is in the data region.
  • A Fortran 90 automatic array is in the stack region.
• C/C++ code:
  • Static C data is in the data region.
  • Automatic C data is in the stack region.
  • C data allocated through malloc is in the data region.

At Indiana University, if you have a question about program segments, contact the UITS Research Applications and Deep Learning team.