Character types

Open Client has four character types, CS_CHAR, CS_LONGCHAR, CS_VARCHAR, and CS_UNICHAR:

CS_CHAR corresponds to the Adaptive Server types char and varchar. That is, Client-Library interprets both the server char and varchar types as CS_CHAR. For example, ct_describe returns CS_CHAR_TYPE when describing a result column that has the server datatype varchar.

CS_CHAR is defined as:
```
typedef char    CS_CHAR;
```
WARNING! CS_LONGCHAR and CS_VARCHAR do not correspond to any Adaptive Server datatypes. Specifically, CS_VARCHAR does not correspond to the Adaptive Server datatype varchar.
CS_LONGCHAR does not correspond to any Adaptive Server type, but some Open Server applications support CS_LONGCHAR. An application uses the CS_DATA_LCHAR capability to determine whether an Open Server connection supports CS_LONGCHAR. If it does, then ct_describe returns CS_LONGCHAR when describing a result data item.

A CS_LONGCHAR value has a maximum length of 2,147,483,647 bytes. CS_LONGCHAR is defined as:
```
typedef unsigned char    CS_LONGCHAR;
```
CS_VARCHAR does not correspond to any Adaptive Server type. For this reason, Open Client routines do not return CS_VARCHAR_TYPE. CS_VARCHAR is provided to enable non-C programming language veneers to be written for Open Client. Typical client applications will not use CS_VARCHAR.

CS_VARCHAR is defined as:
```
typedef struct _cs_varchar
```
```
 {
```
```
     CS_SMALLINT      len;
```
```
     CS_CHAR          str[CS_MAX_CHAR];
```
```
 } CS_VARCHAR;
```
where:
- len is the length of the string.
- str is the string itself. Note that str is not null-terminated.
  
  Although CS_VARCHAR variables are used to store variable-length values, CS_VARCHAR is considered to be a fixed-length type. This means that an application does not typically need to provide Client-Library with the length of a CS_VARCHAR variable. For example, ct_bind ignores the value of datafmt−>maxlength when binding to a CS_VARCHAR variable.
- CS_UNICHAR corresponds to the Adaptive Server unichar fixed-width and univarchar variable-width datatypes. CS_UNICHAR is a shared, C-programming datatype that can be used anywhere the CS_CHAR datatype is used. The CS_UNICHAR datatype stores character data in the two-byte Unicode UTF-16 format.
  
  CS_UNICHAR is defined as follows:
```
typedef unsigned char       CS_UNICHAR;  
```