Why is(S1)fun?What delights may its practitioner expect as his reward?First inthe sheer joy of making things．As the child delights in his mud pie，SO the aduIt enjoys buildingthings，especially things of his own design．Second is the pleasure of making things that are usefulto other people.Third is the fascination of fashioning complex puzzle—like objects of interlockingmoving parts and watching them work in subtle cycles，playing out the consequences 0f pfineiplesbuilt in from the beginning．Fourth is the joy of always learning，which spfings from the(S2)——nature of the task．In one way or another the problem is ever new，arid its solver leams some．thing：sometimes (S3)． sometimes theoretical，and sometimes both．Finallv．there is thedelight of working in such a tractable medium．The(S4)，like the poet，works 0nly slightlyremoved from pure thought—stuff． Few media of creation are so flexible，SO easy to polish and rework，SO readily capable of realizing grand conceptual structures．Yet the program(S5)，unlike the poet’s words，is real in the sense that it moves andworks，producing visible outputs separate from the construct itself．It prints resuhs，draws pictures．produces sounds，moves arms．Programming then is fun because it gratifies creative longings builtdeep within US and delights sensibilities we have in common with all men．

(S1)

A．programming

B．composing

C．WOrking

D．writing