out.dat

c语言小程序100个

n any field.Yu can create an index   
rrect record.yu have the c  
n several fields t be usedYu can create an index n any field,     
n parts theref, that you want t use as a key. Thetgether, r      
u quick access t specific records and definekeys in indexes allw y   
f a ISAM file. After yu no longerrders fr sequential prcessing      
n and indexes have no effectneed an index, yu can delete it. Additi  
rds or on other indexes.n the data rec  
rd to uniquely identify thatYu may want a field in field in each rec  
yeerecrd frm all ther recrds in the file. Fr example, the Empl      
 not assign the same number t twoNumber field is unique if yu d   
 otherdifferent emplyees, and you never reassign these numbers t  
 find r modify the recrd belonging to aemplyees. If yu wish t     
uble of determiningspecific emplyee, this unique field saves the th  
rrect record.whether yu have the c  
rdIf yu do nt have a unique field, yu must find the first rec    
rd is the one youthe matches yur key and determine whether the rec  
thers.want. If it is nt the crrect one, yu must search again t find      
ur records, youIf yu know that yu have a unique field within y   
n, and ISAM will allow onlycan include this fact in the key descripti 
yee numbers areunique keys. Fr example, if yu specify that the empl   
u add recrds to the file for, r changeunique, ISAM nly lets y    
yee numbers that d not alreadly exist int file. numbers t, empl