This is an example from www.keil.com/.../configWizard.html
// <o TIMESTAMP_SRC>Time Stamp Source // <dwt=> DWT Cycle Counter // <systick=> SysTick // <user=> User Timer // Selects source for 32-bit time stamp #define TIMESTAMP_SRC systick
Try inserting a digit into both instances of "TIMESTAMP_SRC", for example "TIMESTAMP2_SRC" and the parser will fail with "Syntax error in Options Block - line xxx: Invalid numeric number." Pregrammers very frequently use #defined values with digits and this is a severe limitation.