c++ - typedef for an array of structures with one char array as member for structure -

i declare variable in oracle-pro *c/c++ by

varchar myvar[25]; 

after precompilation of file changes this

typedef struct { unsigned short len; unsigned char arr[1]; } varchar; struct { unsigned short len; unsigned char arr[25]; } myvar; 

since typedef given varchar when use varchar myvar[25] statement,

1. why not create array of structures myvar[25] ?
2. how arr[1] in typedef statement changed arr[25] in second line?

from precompiled code showed,

varchar myvar[25]; 

is interpreted sql

myvar varchar(25) 

which generated, notice char arr[25]

struct { unsigned short len; unsigned char arr[25]; } myvar;