Conditional compilation-several common formats

When analyzing the daily embedded logic program, when encountering conditions, my mind suddenly cannot bend over. Now I will review the "Conditional compilation: conditional compilation is commonly used in the following formats: 1. # ifdef identifier program segment 1 # else program segment 2 # endif function: if the specified identifier has been defined by # define, compile program segment 1 in the program compilation phase; otherwise, compile the program segment 2. 2. # ifndef identifier program segment 1 # else program segment 2 # endif function :( clever and ifdef are opposite) if the specified identifier is not defined by # define, compile program segment 1 in the program compilation phase; otherwise, compile the program segment 2. 3. # if expression Section 1 # else section 2 # endif function: Compile Section 1 when the specified expression value is true (not 0); otherwise, compile section 2. The following section describes how to compile the application conditions in the program: [html] # if (LCD _Type = LCDW35) | (LCD _Type = LCDS35 )) // 3.5 inch screen extern unsigned char TQ_LOGO_320240 []; // custom image # elif (LCD _Type = LCDT35) // 3.5 inch screen extern unsigned char TQ_LOGO_240320 []; // custom image # elif (LCD _Type = LCDW43) // 3.5-inch screen extern unsigned char TQ_LOGO_480272 []; // custom image # elif (LCD _Type = VGA) // VGA extern unsigned char tq_logo_6401_[]; // custom image # elif (LCD _Type = LCDA70) // 7-inch screen extern unsigned char tq_logo_8001_[]; // custom image # endif