Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
166 words
Display system comprising a symbol table (20, 20ʹ, 20ʺ) in general purpose storage (22) which includes blocks of data forming symbol definitions for each of a set of symbols forming a desired symbol set, an all points addressable (APA) display buffer (30) which includes on-screen APA storage (32) for data indicative of pels to be displayed on a screen and off-screen APA storage (34) for symbol definitions, and buffer control logic for associating symbol definitions in off-screen APA storage with locations in on-screen APA storage such that symbols are displayed at desired locations on the display screen, wherein the display system additionally comprises cache control logic (42) for copying the definition of a symbol for display from the symbol table (20, 20ʹ, 20ʺ) in general purpose storage (22) to off-screen APA storage (34) if the definition for the selected symbol is not already held in off-screen APA storage (34), whereby the off-screen APA storage (34) is configured as a cache for holding definitions for selected symbols.
Claim 2
Dependent Claim
166 words
Display system comprising a symbol table (20, 20ʹ, 20ʺ) in general purpose storage (22) which includes blocks of data forming symbol definitions for each of a set of symbols forming a desired symbol set, an all points addressable (APA) display buffer (30) which includes on-screen APA storage (32) for data indicative of pels to be displayed on a screen and off-screen APA storage (34) for symbol definitions, and buffer control logic for associating symbol definitions in off-screen APA storage with locations in on-screen APA storage such that symbols are displayed at desired locations on the display screen, wherein the display system additionally comprises cache control logic (42) for copying the definition of a symbol for display from the symbol table (20, 20ʹ, 20ʺ) in general purpose storage (22) to off-screen APA storage (34) if the definition for the selected symbol is not already held in off-screen APA storage (34), whereby the off-screen APA storage (34) is configured as a cache for holding definitions for selected symbols.
Claim 3
Dependent Claim
77 words
A display system as claimed in claim 1 additionally comprising a cache table (40) in general purpose storage (22) comprising an entry for each symbol in the symbol set for pointing to the location in off-screen APA storage (34), if any, at which the corresponding symbol definition is held, each entry in the cache table (40) also being associated with the location in the symbol table (20, 20ʹ, 20ʺ) at which the corresponding symbol definition is stored.
Claim 4
Dependent Claim
65 words
A display system as claimed in claim 2 wherein a plurality of symbol tables (20, 20ʹ, 20ʺ) for different symbol sets are stored in general purpose storage (22) and wherein the display system is provided with pointer means (24) under the control of the cache control logic (42) for associating the cache table (40) with the symbol table (eg 20) for the desired symbol set.
Claim 5
Dependent Claim
196 words
A display system as claimed in either claim 3 in which the cache control logic (42) is arranged to interrogate the cache table (40) when a selected symbol is to be added to the display in order to identify the location, if any, at which the definition for the selected symbol is held in off-screen APA storage (34), and if the symbol definition is so held, to cause the buffer control logic to associate the selected symbol definition in off-screen APA storage (34) with on-screen APA storage (32) such that the symbol displayed at a desired location on the display screen, otherwise to copy the definition for the selected symbol from the appropriate symbol table entry in general purpose storage to a free location in off-screen APA storage (34), to store an indication in the appropriate entry in the cache table (40) of the location in off-screen APA storage (34) at which the definition for that symbol is now held and to cause the buffer control logic to associate the selected definition in off-screen APA (34) storage with on-screen APA storage (32) such that the symbol is displayed at the desired location on the display screen.
Claim 6
Dependent Claim
53 words
A display system as claimed in any one of the preceding claims wherein the buffer control logic comprises block logic (36) for copying the definitions for symbols to be displayed from off-screen APA storage (34) to on-screen APA storage (32) such that the symbols are displayed at desired locations on the display screen.
Claim 7
Dependent Claim
71 words
A display system as claimed in any one of claims 1 to 4 wherein the buffer control logic comprises means for storing pointers (321, 322, 323) in on-screen APA storage (32) to symbol definitions in off-screen APA storage (34) and merge control logic (37) for merging data from on-screen and off-screen APA storage for controlling the display such that the symbols are displayed at a desired locations on the display screen.