C:\MIX\firebird\oldfb156\bin\isql.exe localhost/3156:C:\MIX\firebird\db156.fdb -ch win1252

Statement failed, SQLCODE = -924

bad parameters on attach or create database
Use CONNECT or CREATE DATABASE to specify a database

SQL> connect 'localhost/3156:C:\MIX\firebird\db156.fdb';
Database:  'localhost/3156:C:\MIX\firebird\db156.fdb'
SQL> show version;
ISQL Version: WI-V1.5.6.5026 Firebird 1.5
Firebird/x86/Windows NT (access method), version "WI-V1.5.6.5026 Firebird 1.5"
Firebird/x86/Windows NT (remote server), version "WI-V1.5.6.5026 Firebird 1.5/tcp (csprog)/P10"
Firebird/x86/Windows NT (remote interface), version "WI-V1.5.6.5026 Firebird 1.5/tcp (csprog)/P10"
on disk structure version 10.1
SQL> show database;
Database: localhost/3156:C:\MIX\firebird\db156.fdb
        Owner: SYSDBA
PAGE_SIZE 16384
Number of DB pages allocated = 9386
Sweep interval = 0
Forced Writes are OFF
Transaction - oldest = 2471
Transaction - oldest active = 2472
Transaction - oldest snapshot = 2472
Transaction - Next = 2476
Default Character set: NONE

C:\MIX\firebird\oldfb156\bin>isql -?
Unknown switch: ?
isql [<database>] [-e] [-t <terminator>] [-i <inputfile>] [-o <outputfile>]
     [-x|-a] [-d <target db>] [-u <user>] [-p <password>]
     [-page <pagelength>] [-n] [-m] [-q] [-s <sql_dialect>]
     [-r <rolename>] [-c <num cache buffers>] [-z] -nowarnings -noautocommit