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True, it is difficult to tell or spot some minor error. Any compiler give u more precise information on what the problem is. Also it will show u which line is problematic. With this info, if u still not able to fix, u can paste the error here, and people and help u from there
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these are the errors
Error (10500): VHDL syntax error at carpark.vhd(10) near text "q"; expecting "end", or "begin", or a declaration statement
Error (10500): VHDL syntax error at carpark.vhd(10) near text ")"; mismatched closing parenthesis
Error (10523): Ignored construct carpark at carpark.vhd(3) due to previous errors
Error (10500): VHDL syntax error at carpark.vhd(18) near text "type"; expecting ";", or "is"
Error (10500): VHDL syntax error at carpark.vhd(24) near text "elsif"; expecting "end", or "(", or an identifier ("elsif" is a reserved keyword), or a sequential statement
Error (10500): VHDL syntax error at carpark.vhd(24) near text "then"; expecting "(", or "'", or "."
Error (10500): VHDL syntax error at carpark.vhd(26) near text "if"; expecting "process"
Error (10500): VHDL syntax error at carpark.vhd(34) near text "begin"; expecting "end", or "(", or an identifier ("begin" is a reserved keyword), or a sequential statement
Error (10500): VHDL syntax error at carpark.vhd(36) near text "with"; expecting "end", or "(", or an identifier ("with" is a reserved keyword), or a sequential statement
Error (10500): VHDL syntax error at carpark.vhd(37) near text "when"; expecting ";"
Error (10500): VHDL syntax error at carpark.vhd(55) near text "if"; expecting "process"
Error (10396): VHDL syntax error at carpark.vhd(57): name used in construct must match previously specified name "arc"
Info: Found 0 design units, including 0 entities, in source file carpark.vhd
Error: Quartus II Analysis & Synthesis was unsuccessful. 12 errors, 0 warnings
Error: Peak virtual memory: 222 megabytes
Error: Processing ended: Wed Jul 31 22:10:50 2013
Error: Elapsed time: 00:00:04
Error: Total CPU time (on all processors): 00:00:03
Error: Quartus II Full Compilation was unsuccessful. 14 errors, 0 warnings