Keithley 2651A Reference Manual page 278

Section 6: Instrument programming
String library functions
Function
string.upper(s)
6-34
Model 2651A High Power System SourceMeter® Instrument Reference Manual
Description
Receives a string and returns a copy of this string with all
lowercase letters changed to uppercase. All other characters are
left unchanged. The definition of what a lowercase letter is
depends on the current locale.
2651A-901-01 Rev. A / March 2011