States and State Lists
This chapter deals with states of GKS and data structures describing them. The operating states of GKS are a central concept within GKS which forces a strict structure in graphics programming For example, a workstation can be accessed only after a certain sequence of initialising functions have been invoked; output can be generated only after a workstation has been activated; workstation attributes can be set only after the workstation has been allocated. Therefore, the novice reader should read carefully Section 3.2 and 3.3 where the different operating states are introduced and those functions are listed which are allowed in the respective operating states. Section 3.4 describes the content of some state lists. It aims primarily at implementors and experienced users of GKS. Section 3.5 introduces the first two GKS functions: OPEN GKS and CLOSE GKS.
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