Differences

Difference between REFRESH; FREE; CLEAR

REFRESH : If REFRESH is applied on an internal table  then the entries in the table will be deleted but the memory allocated to that table still exists.

FREE : If FREE is applied on an internal table then the memory allocated to that table will not exist and that memory can be used by some other variable/object.In this case both the entries and the memory do not exist anymore.

CLEAR : pplied on If CLEAR is generally used for workareas and also, if the internal table is defined with header line, clear can be applied to clear the header line. The memory allocated to it is not removed.

Difference between CHECK and IF

if the IF condition is not satisfied control will go to the next statements. Here when the IF condition is used, and the condition is not satisfied, control looks for remaining executable lines inside the loop.

in case of CHECK if the condition is not satisfied control will; not go further.Here when the CHECK condition is used, and the condition is not satisfied, control comes outside the loop.