BBC BASIC Programmers' Reference

by Richard Russell, October 2011

The code listed below reports, once per second, the current total CPU usage:

        *FLOAT 64
 
        DIM IdleTime{l%,h%}, KernelTime{l%,h%}, UserTime{l%,h%}
 
        idletime = 0
        kerneltime = 0
        usertime = 0
        REPEAT
          WAIT 100
          SYS "GetSystemTimes", IdleTime{}, KernelTime{}, UserTime{}
 
          oldidletime = idletime
          oldkerneltime = kerneltime
          oldusertime = usertime
          idletime = IdleTime.h% * 2^32 + (IdleTime.l% >>> 1)*2
          kerneltime = KernelTime.h% * 2^32 + (KernelTime.l% >>> 1)*2
          usertime = UserTime.h% * 2^32 + (UserTime.l% >>> 1)*2
 
          idledelta = idletime-oldidletime
          kerneldelta = kerneltime-oldkerneltime
          userdelta = usertime-oldusertime
 
          cpuusage = (userdelta+kerneldelta-idledelta)/(userdelta+kerneldelta)
          PRINT "CPU usage = ";INT(100*cpuusage+0.5) "%"
 
        UNTIL FALSE