为什么在keil中创建目标文件的时候总是出现syntax error '_7'??错误指在p3_7=3_7 行

#include <REGX51.H>
void delay(unsigned char n); //函数delay()存在 文件delay.c
中
code unsigned song[]={
0x82,0x01,0x81,0x94,0x84,0xB4,0xA4,0x04,0x82,0x01,0x81,
0x94,0x84,0xC4,0xB4,0x04, 0x82,0x01,0x81,0xF4,0xD4,0xB4,
0xA4,0x94,0xE2,0x01,0xE1,0xD4,0xB4,0xC4,0xB4,0x04,
0x82,0x01,0x81,0x94,0x84,0xB4,0xA4,0x04,0x82,0x01,0x81,
0x94,0x84,0xC4,0xB4,0x04, 0x82,0x01,0x81,0xF4,0xD4,0xB4,
0xA4,0x94,0xE2,0x01,0xE1,0xD4,0xB4,0xC4,0xB4,0x04,
0x00};
code int note[]={
0x0000,0xFB03,0xFB8E,0xFC0B,0xFC43,0xFCAB,0xFD08,0xFD32,

0xFD81,0xFDC7,0xFE05,0xFE21,0xFE55,0xFE83,0xFE99,0xFEC0};
unsigned char i=0;
unsigned char hi_note,low_note;
static void timer1_isr(void) interrupt TF1_VECTOR using 2
{
TR1=0;
TL1=low_note;
TH1=hi_note;
TR1=1;
P3_7=3_7;
}
static void timer1_initialize(void)
{
EA=0;
TR1=0;
TMOD = 0X10;
ET1=1;
EA=1;
}
void singing()