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; this is installed in memory by the transient part of SvarCOM. it has only
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; this is installed in memory by the transient part of SvarCOM. it has only
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; two jobs: providing a resident buffer for command history, environment, etc
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; two jobs: providing a resident buffer for command history, environment, etc
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; and respawning COMMAND.COM whenever necessary.
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; and respawning COMMAND.COM whenever necessary.
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CPU 8086
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CPU 8086
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org 0x100
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org 0h           ; this is meant to be executed without a PSP
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PSP_ENVSEG equ 0x2C
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section .text    ; all goes into code segment
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section .text    ; all goes into code segment
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                 ; offset
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                 ; offset
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SIG1 dw 0x1983   ;  +0
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SIG1 dw 0x1983   ;  +0
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mov dx, COMSPECBOOT
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mov dx, COMSPECBOOT
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; do I have a valid COMSPEC?
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; do I have a valid COMSPEC?
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or [COMSPECPTR], word 0
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or [COMSPECPTR], word 0
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jz USEDEFAULTCOMSPEC
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jz USEDEFAULTCOMSPEC
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; set ES:DX to actual COMSPEC
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; set ES:DX to actual COMSPEC (in env segment)
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mov es, [ENVSEG]
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mov es, [PSP_ENVSEG]
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mov dx, [COMSPECPTR]
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mov dx, [COMSPECPTR]
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USEDEFAULTCOMSPEC:
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USEDEFAULTCOMSPEC:
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; prepare the exec param block
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; prepare the exec param block
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mov ax, [ENVSEG]
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mov ax, [PSP_ENVSEG]
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mov [EXEC_PARAM_REC], ax
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mov [EXEC_PARAM_REC], ax
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mov ax, CMDTAIL
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mov ax, CMDTAIL
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mov [EXEC_PARAM_REC+2], ax
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mov [EXEC_PARAM_REC+2], ax
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mov [EXEC_PARAM_REC+4], cs
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mov [EXEC_PARAM_REC+4], cs
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