# Q* \: q" M9 V5 ? k1 v. I</FONT></P>8 C$ T. @! y; U! `: U# r
<><FONT color=#ff0000>函数名: keep </FONT><FONT color=#0000ff>- c8 {% e( }% k# ?) y
<FONT color=#000000>功 能: 退出并继续驻留 : f1 Q, _( k V) e- e用 法: void keep(int status, int size); - M+ I# v2 n% I' u; ?3 m1 ]程序例: </FONT></FONT></P>2 _& `% i; V0 Y" L
<><FONT color=#0000ff>/***NOTE: 7 J& b: k5 b* e2 _
This is an interrupt service routine. You 6 a7 t7 L2 ~6 _' V$ w9 u: hcan NOT compile this program with Test 2 `* u9 e) x$ g; Y6 f' k5 {$ ^
Stack Overflow turned on and get an ! s; J, [4 p4 d8 K+ l* uexecutable file which will operate " i7 U- q2 j1 O% J! ?& g) _: V6 J* ~
correctly. Due to the nature of this z; ~$ S! U& W4 Y# Y2 b) Cfunction the formula used to compute : c5 j, ~ u( c! Nthe number of paragraphs may not / {/ z/ W+ q/ A. Q4 K: D" O1 ~necessarily work in all cases. Use with 1 j; @5 h) r9 h, D# a4 @6 t
care! Terminate Stay Resident (TSR) * K0 |! n6 N. Q2 i
programs are complex and no other support : x0 b" r( d& E% Z2 k) _
for them is provided. Refer to the $ C/ y( q+ g6 T+ q2 I& cMS-DOS technical documentation % Y" d5 U. z4 m
for more information. */ $ e/ p. H8 z2 i3 W% g#include <DOS.H> 4 j5 B5 V7 b; s0 o$ R/* The clock tick interrupt */ ) M* e9 J/ ?3 G9 A; Y1 |; q
#define INTR 0x1C ) U8 a) ]. P o# G/* Screen attribute (blue on grey) */ + P6 j) I( O+ I- S; K
#define ATTR 0x7900 </FONT></P> * @- E3 U/ Q( P# x4 v+ o<><FONT color=#0000ff>/* reduce heaplength and stacklength @$ K( ~6 T, w a) G
to make a smaller program in memory */ 5 w5 m2 x; l4 k t0 \8 @7 L" Q
extern unsigned _heaplen = 1024; 3 t6 g9 X/ l& H% Oextern unsigned _stklen = 512; </FONT></P> ! I( ^ H! p! O) @<><FONT color=#0000ff>void interrupt ( *oldhandler)(void); </FONT></P> - z7 q% K, t) J. O7 p<><FONT color=#0000ff>void interrupt handler(void) / O0 e, _2 X" K% A" `{ 5 O' r, o6 R& k' l) L2 V% Punsigned int (far *screen)[80]; # G& y/ I2 L% W* h2 Ostatic int count; </FONT></P> 0 m, W; ]! c% S0 P" U. u<><FONT color=#0000ff>/* For a color screen the video memory ( s2 G! V! i- l* B
is at B800:0000. For a monochrome . D( W/ j: |, n! |7 e2 Gsystem use B000:000 */ 4 P q' E7 i, e1 V- L1 K* o# Rscreen = MK_FP(0xB800,0); </FONT></P>/ d& e0 C4 [6 S p+ P- T5 L
<><FONT color=#0000ff>/* increase the counter and keep it # R2 k& u) {/ ]8 ~, r3 O) qwithin 0 to 9 */ ) Z" z7 D" j. h! a
count++; 4 _8 W* l" ]! y% K
count %= 10; </FONT></P> ) ?2 I- t0 g9 S$ T2 B) K<><FONT color=#0000ff>/* put the number on the screen */ / T# f/ N f+ p P* U: {, ]6 |1 v
screen[0][79] = count + '0' + ATTR; </FONT></P>) x$ s5 n5 m1 M/ l7 ?2 w
<P><FONT color=#0000ff>/* call the old interrupt handler */ & E1 \% S( K7 w A% x; f3 h: K* ]
oldhandler(); 6 u# e6 [9 E$ p} </FONT></P>2 g5 V! O( B% S
<P><FONT color=#0000ff>int main(void) 8 @' ^" ?/ P1 ]$ x' |4 f2 w2 b
{ </FONT></P> ( K8 j) C D2 U: G: U/ E<P><FONT color=#0000ff>/* get the address of the current clock ! b- P0 g# v; u) n
tick interrupt */ ( @1 A# q* @7 h. r2 @7 Foldhandler = getvect(INTR); </FONT></P> ( F7 g% y- ~! ~5 y! h<P><FONT color=#0000ff>/* install the new interrupt handler */ h6 Q( _4 }2 e' a6 y) K
setvect(INTR, handler); </FONT></P>6 O g/ f+ |. k9 X% k
<P><FONT color=#0000ff>/* _psp is the starting address of the 7 R6 F# g$ B) T, U5 Aprogram in memory. The top of the stack + G* m5 |0 @( L) H9 K& fis the end of the program. Using _SS and ! a, f( T; v7 I9 s9 Q+ E_SP together we can get the end of the h: }- b! \9 |6 ostack. You may want to allow a bit of ( o/ x1 R* ~! P* N
saftey space to insure that enough room L E5 Y9 N( j$ V* d. w4 p
is being allocated ie: 8 X2 F/ T( H0 n; C% Z
(_SS + ((_SP + safety space)/16) - _psp) . l* V) Y) r& l5 `
*/ F0 l! a0 E7 W4 t0 I8 M( L# Kkeep(0, (_SS + (_SP/16) - _psp)); 4 I; U7 S' K0 `! k/ yreturn 0; : u$ a5 E7 A" N" O W}</FONT></P>