==== 7.5.17 dup ====

Duplicate top operand stack word 

Format 

dup 

Forms 

dup = 61 (0x3d) 

Stack 

..., word -> ..., word, word 

Description 

The top word on the operand stack is duplicated and pushed onto the operand stack. 

The dup instruction must not be used unless word contains a 16-bit data type. 

Notes 

Except for restrictions preserving the integrity of 32-bit data types, the dup instruction operates on an untyped word, ignoring the type of data it contains.