How does one write an OCI program?

Look at this very basic sample Oracle OCI8 program:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <oci.h>

#pragma comment(lib, "d:\orant\oci80\lib\msvc\ora803.lib")

static OCIEnv           *p_env;
static OCIError         *p_err;
static OCISvcCtx        *p_svc;
static OCIStmt          *p_sql;
static OCIDefine        *p_dfn    = (OCIDefine *) 0;
static OCIBind          *p_bnd    = (OCIBind *) 0;

void main()
{
   int             p_bvi;
   char            p_sli[20];
   int             rc;
   char            errbuf[100];
   int             errcode;

   rc = OCIInitialize((ub4) OCI_DEFAULT, (dvoid *)0,  /* Initialize OCI */
           (dvoid * (*)(dvoid *, size_t)) 0,
           (dvoid * (*)(dvoid *, dvoid *, size_t))0,
           (void (*)(dvoid *, dvoid *)) 0 );

   /* Initialize evironment */
   rc = OCIEnvInit( (OCIEnv **) &p_env, OCI_DEFAULT, (size_t) 0, (dvoid **) 0 );

   /* Initialize handles */
   rc = OCIHandleAlloc( (dvoid *) p_env, (dvoid **) &p_err, OCI_HTYPE_ERROR,
           (size_t) 0, (dvoid **) 0);
   rc = OCIHandleAlloc( (dvoid *) p_env, (dvoid **) &p_svc, OCI_HTYPE_SVCCTX,
           (size_t) 0, (dvoid **) 0);

   /* Connect to database server */
   rc = OCILogon(p_env, p_err, &p_svc, "scott", 5, "tiger", 5, "d458_nat", 8);
   if (rc != 0) {
      OCIErrorGet((dvoid *)p_err, (ub4) 1, (text *) NULL, &errcode, errbuf, (ub4) sizeof(errbuf), OCI_HTYPE_ERROR);
      printf("Error - %.*sn", 512, errbuf);
      exit(8);
   }

   /* Allocate and prepare SQL statement */
   rc = OCIHandleAlloc( (dvoid *) p_env, (dvoid **) &p_sql,
           OCI_HTYPE_STMT, (size_t) 0, (dvoid **) 0);
   rc = OCIStmtPrepare(p_sql, p_err, "select ename from emp where deptno=:x",
           (ub4) 37, (ub4) OCI_NTV_SYNTAX, (ub4) OCI_DEFAULT);

   /* Bind the values for the bind variables */
   p_bvi = 10;     /* Use DEPTNO=10 */
   rc = OCIBindByName(p_sql, &p_bnd, p_err, (text *) ":x",
           -1, (dvoid *) &p_bvi, sizeof(int), SQLT_INT, (dvoid *) 0,
           (ub2 *) 0, (ub2 *) 0, (ub4) 0, (ub4 *) 0, OCI_DEFAULT);

   /* Define the select list items */
   rc = OCIDefineByPos(p_sql, &p_dfn, p_err, 1, (dvoid *) &p_sli,
           (sword) 20, SQLT_STR, (dvoid *) 0, (ub2 *)0,
           (ub2 *)0, OCI_DEFAULT);

   /* Execute the SQL statment */
   rc = OCIStmtExecute(p_svc, p_sql, p_err, (ub4) 1, (ub4) 0,
           (CONST OCISnapshot *) NULL, (OCISnapshot *) NULL, OCI_DEFAULT);

   while (rc != OCI_NO_DATA) {             /* Fetch the remaining data */
      printf("%sn",p_sli);
      rc = OCIStmtFetch(p_sql, p_err, 1, 0, 0);
   }

   rc = OCILogoff(p_svc, p_err);                           /* Disconnect */
   rc = OCIHandleFree((dvoid *) p_sql, OCI_HTYPE_STMT);    /* Free handles */
   rc = OCIHandleFree((dvoid *) p_svc, OCI_HTYPE_SVCCTX);
   rc = OCIHandleFree((dvoid *) p_err, OCI_HTYPE_ERROR);

   return;
}